[libcxx] [libcxxabi] [libunwind] [llvm] [libcxxabi][libunwind] Support for using LLVM libc (PR #134893)

[Petr Hosek via llvm-commits]

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@@ -311,7 +313,7 @@ endif()
 
 add_library(cxxabi_static STATIC)
 if (LIBCXXABI_USE_LLVM_UNWINDER AND NOT LIBCXXABI_STATICALLY_LINK_UNWINDER_IN_STATIC_LIBRARY)
-  target_link_libraries(cxxabi_static PUBLIC unwind_static)
+  target_link_libraries(cxxabi_static PUBLIC unwind_static runtimes-libc-static)
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petrhosek wrote:

I expect this is eventually going to come up but there's additional complexity we'll need to figure out: `libc.a` that's intended for static linking could be compiled as `-fPIE` but `libc.a` that's intended for linking into shared libraries (such as `libc++abi.so` or `libc++.so`) must be compiled as `-fPIC`.

https://github.com/llvm/llvm-project/pull/134893