[clang] [compiler-rt] [libcxx] [libunwind] [llvm] [openmp] [runtimes] remove workaround for old CMake when setting `--unwindlib=none` (PR #93429)

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h-vetinari wrote:

I think the riddle may be explained by @mstorsjo's excellent commit message from https://github.com/llvm/llvm-project/commit/4169b5251f58cc0eb2ac6c3b4b9990a51728aac6 (which I just found):
> If the CMake requirement is bumped to 3.14, we could use
`CMAKE_REQUIRED_LINK_OPTIONS` instead, removing the need for the
`--{start,end}-no-unused-arguments` options. (However, do note that
`CMAKE_REQUIRED_LINK_OPTIONS` is problematic in combination with
`CMAKE_TRY_COMPILE_TARGET_TYPE` set to `STATIC_LIBRARY`; see
https://gitlab.kitware.com/cmake/cmake/-/issues/23454.)

... which is indeed what libunwind specifies:
https://github.com/llvm/llvm-project/blob/6859685a87ad093d60c8bed60b116143c0a684c7/libunwind/CMakeLists.txt#L224

https://github.com/llvm/llvm-project/pull/93429