Trying to document how I built Elm Platform on FreeBSD 11.1

build-elm-platform-on-freebsd-11-1.sh

# make sure lzlib exists on system.
# run `pkg install lzlib`
# this is the only step that required superuser privileges.

# USAGE
# For building at <PREFIX>/Elm-Platform/<VERSION>, run:
# sh build-elm-platform-on-freebsd-11-1.sh <PREFIX> <VERSION>

# SIDE EFFECTS
# Blindly downloads ghc 7.10.2, keeps it beside Elm-Platform in <PREFIX>
# creates a directory `work` where the script is run.
# (run it inside an empty directory to avoid clobbering files)

mkdir work
pushd work

git clone https://github.com/elm-lang/elm-platform.git

wget 'https://downloads.haskell.org/~ghc/7.10.2/ghc-7.10.2-x86_64-portbld-freebsd.tar.xz'
tar xJf ghc-7.10.2-x86_64-portbld-freebsd.tar.xz

pushd ghc-7.10.2
./configure --prefix="$1/ghc/7.10.2"
gmake install
popd

pushd "$1"
export PATH="$1/ghc/7.10.2/bin:$1/Elm-Platform/$2/.cabal-sandbox/bin:$PATH"
runhaskell $OLDPWD/elm-platform/installers/BuildFromSource.hs $2
popd

popd

# Please comment here If this worked for you.