Haskell Cloud Build to Heroku

cloudbuild.heroku.yaml

steps:                                                                                                                                                                                                                            
  - name: 'gcr.io/cloud-builders/docker'                                                                                                                                                                                          
    args: [ 'pull', 'gcr.io/$PROJECT_ID/builder-api.dungeon.studio' ]                                                                                                                                                             
                                                                                                                                                                                                                                  
  - name: 'gcr.io/cloud-builders/docker'                                                                                                                                                                                          
    args: [ 'pull', 'gcr.io/$PROJECT_ID/api.dungeon.studio' ]                                                                                                                                                                     
                                                                                                                                                                                                                                  
  - name: 'gcr.io/cloud-builders/docker'                                                                                                                                                                                          
    args: [ 'build',                                                                                                                                                                                                              
            '--cache-from', 'gcr.io/$PROJECT_ID/builder-api.dungeon.studio',                                                                                                                                                      
            '--cache-from', 'gcr.io/$PROJECT_ID/api.dungeon.studio',                                                                                                                                                              
            '-t', '$_IMAGE_NAME',                                                                                                                                                                                                 
            '-f', 'Dockerfile', '.' ]                                                                                                                                                                                             
                                                                                                                                                                                                                                  
  - name: 'gcr.io/cloud-builders/docker'                                                                                                                                                                                          
    args: [ 'login', '--username=_', '--password=$_HEROKU_API_KEY', 'registry.heroku.com' ]                                                                                                                                       
                                                                                                                                                                                                                                  
images:                                                                                                                                                                                                                           
  - '$_IMAGE_NAME'                                                                                                                                                                                                                
                                                                                                                                                                                                                                  
timeout: 60m

Dockerfile

FROM alpine:3.7 as builder                                                                                                                                                                                                        
MAINTAINER Alex Brandt <alunduil@alunduil.com>                                                                                                                                                                                    
                                                                                                                                                                                                                                  
RUN apk add --no-cache musl-dev zlib-dev                                                                                                                                                                                          
RUN apk add --no-cache cabal ghc                                                                                                                                                                                                  
                                                                                                                                                                                                                                  
WORKDIR /usr/local/src/api.dungeon.studio                                                                                                                                                                                         
                                                                                                                                                                                                                                  
RUN cabal update                                                                                                                                                                                                                  
                                                                                                                                                                                                                                  
COPY ./*.cabal ./                                                                                                                                                                                                                 
RUN cabal install -j --only-dependencies                                                                                                                                                                                          
                                                                                                                                                                                                                                  
COPY . ./                                                                                                                                                                                                                         
RUN cabal build -j --ghc-options="-static -optc-static -optl-static -optl-pthread"                                                                                                                                                
                                                                                                                                                                                                                                  
FROM alpine:3.7                                                                                                                                                                                                                   
MAINTAINER Alex Brandt <alunduil@alunduil.com>                                                                                                                                                                                    
                                                                                                                                                                                                                                  
RUN apk add --no-cache ca-certificates                                                                                                                                                                                            
                                                                                                                                                                                                                                  
COPY --from=builder /usr/local/src/api.dungeon.studio/dist/build/api-dungeon-studio/api-dungeon-studio /                                                                                                                          
                                                                                                                                                                                                                                  
ENTRYPOINT [ "/api-dungeon-studio" ]                                                                                                                                                                                              
CMD [ "Thanks Heroku!" ]