Inline function build error using RubyMotion 2.4

DSCMultipartUploader.m

...

NSString * const ContentStringTypeJPEG = @"image/jpeg";
NSString * const ContentStringTypeVideo = @"video/mp4";
inline NSString *stringFromContentType(DSCMultipartContentType contentType)
{
    switch (contentType) {
        case DSCMultipartContentJPEG:
            return ContentStringTypeJPEG;
            break;
        case DSCMultipartContentVideo:
            return ContentStringTypeVideo;
            break;
        default:
            return @"";
            break;
    }
}

...

log.txt

Build vendor/DSCMultipartFramework
Compile vendor/DSCMultipartFramework/DSCMultipartNetworkingRequest.m
Link ./build/iPhoneSimulator-6.0-Development/dscovr.app/dscovr
Undefined symbols for architecture i386:
  "_stringFromContentType", referenced from:
      -[DSCMultipartUploader initWithPath:destinationURL:contentType:] in libDSCMultipartFramework.a(DSCMultipartUploader.m.o)
ld: symbol(s) not found for architecture i386
clang: error: linker command failed with exit code 1 (use -v to see invocation)
rake aborted!
Command failed with status (1): [/Applications/Xcode.app/Contents/Developer...]

Rakefile

# -*- coding: utf-8 -*-
$:.unshift('/Library/RubyMotion/lib')

require 'motion/project/template/ios'
require 'bundler'

Bundler.require

Motion::Project::App.setup do |app|
  ...
  
  app.vendor_project 'vendor/DSCMultipartFramework', :static
  
  ...
end