Swift concurrency back deployment

[Douglas_Gregor]

@allevato

It looks like Xcode's builtin-swiftStdLibTool copies the concurrency runtime using a new --back-deploy-swift-concurrency flag that the standalone executable in XcodeDefault.xctoolchain/usr/bin/swift-stdlib-tool doesn't support (and the source code for that tool on GitHub was last updated 2 years ago). That tool is critical for other build systems like Bazel to bundle the Swift runtime the same way as Xcode does—is there any chance the source code could be updated (and more importantly, the binary in Xcode updated to match)?

Thank you for bringing this up, Tony! I hadn't realized that this tool was in use anywhere. Yes, we can get this tool updated to support the new flag... unless some eager contributor gets a pull request up first ;)

Doug