Work around a bug in swift-stdlib-tool that results in the Swift runtime being bundled whenever the Swift concurrency back-deploy runtime library is bundled

[keith]

The version of swift-stdlib-tool that ships with Xcode 13.4.1 bundles an unnecessary copy of the Swift runtime whenever it bundles the back-deploy version of the Swift concurrency runtime. This is because the back-deploy version of the Swift concurrency runtime contains an @rpath-relative reference to the Swift runtime due to being built with a deployment target that predates the Swift runtime being shipped with operating system. This @rpath-relative reference to the runtime is sufficient for swift-stdlib-tool to believe the runtime also needs to be bundled with the application.

We work around this within swift_stdlib_tool.py by checking whether any of the binaries that we asked swift-stdlib-tool to process have a deployment target that is low enough to require bundling of the Swift runtime. If not, we remove the Swift runtime from the output directory populated by swift-stdlib-tool.

This is a workaround for https://github.com/apple/swift/issues/58271

PiperOrigin-RevId: 461684127 (cherry picked from commit 65852aab324b4862e613566e59ef7215ce9eaafb)

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[keith]

xcode uses an internal version of this tool, so they sidestep this issue, their implementation must have more knowledge of platform specifics, swift-stdlib-tool entirely relies on the rpaths, which are clearly subject to this type of build issue

[thii]

Related: https://github.com/bazelbuild/rules_apple/pull/1396 Maybe revert that first?

[thii]

https://github.com/bazelbuild/rules_apple/pull/1619