macOS toolchains do not work with Xcode new build system

[dan-zheng]

Various errors occur using Swift for TensorFlow macOS toolchains with Xcode's new build system:

[dan-zheng]

The cause is that the Version string in Info.plist provided in toolchains cannot be parsed by Xcode:

$ /Applications/Xcode.app/Contents/MacOS/Xcode Foo.xcodeproj
2019-12-24 15:47:16.618 XCBBuildService[75398:12495542] /Library/Developer/Toolchains/swift-tensorflow-DEVELOPMENT-2019-12-12-a.xctoolchain: warning: failed to load toolchain: 'Version' parse error: Could not parse version component from: 'swift-tensorflow-DEVELOPMENT-2019-12-12-a

This is an issue in the open source utils/build-toolchain script. Someone discovered this issue on the forums but didn't submit a fix.

[dan-zheng]

Fixed in swiftlang/swift#28945.

New macOS toolchain released: https://storage.googleapis.com/swift-tensorflow/mac/swift-tensorflow-DEVELOPMENT-2019-12-23-a-osx.pkg