[clang] [libc] [llvm] [libc][Github] Perform baremetal libc builds (PR #167583)

[Petr Hosek via cfe-commits]

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@@ -0,0 +1,17 @@
+# Expects target triple to be passed as `ARCH_TRIPLE`
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petrhosek wrote:

I'd call the variable `RUNTIMES_TARGET_TRIPLE` since we want to use the `RUNTIMES_` prefix for all runtimes-build related variables.

https://github.com/llvm/llvm-project/pull/167583