Xcode 9 / Swift 4 simple project doesn't compile because of umbrella header

[Steeve Morin]

Hi,

First of all thank you for this tool.

I am trying to build a sample/simple Swift project with xcbuild 32b9fbeb69bfa2682bd0351ec2f14548aaedd554 and running this issue:

  "output": "\/Users\/steeve\/Library\/Developer\/Xcode\/DerivedData\/XcSimpleSwiftFm-audmmjcecdlhglawdvtravtthozg\/Build\/Intermediates\/XcSimpleSwiftFm.build\/Release-iphoneos\/XcSimpleSwiftFm.build\/unextended-module.modulemap:2:19: error: umbrella header 'XcSimpleSwiftFm.h' not found\n  umbrella header \"XcSimpleSwiftFm.h\"\n                  ^\n<unknown>:0: error: could not build Objective-C module 'XcSimpleSwiftFm'\n",
  "exit-status": 1
}

** BUILD FAILED **

The following build commands failed:
    CompileSwiftSources normal armv7 com.apple.xcode.tools.swift.compiler
(1 failure)

I have attached a sample project, which hopefully will help you: XcBuildSimpleFramework.zip

[Steeve Morin]

Seems related to #237