[cmake] Duplicate `{llvm,compiler_rt}_check_linker_flag` for runtime libs and llvm

We previously had a few varied definitions of this floating around. I made the one installed with LLVM handle all the cases, and then made the others use it.

This issue was reported to me in https://reviews.llvm.org/D116521#3248117 as
D116521 made clang and llvm use the common cmake utils.

Reviewed By: sebastian-ne, phosek, #libunwind, #libc, #libc_abi, ldionne

Differential Revision: https://reviews.llvm.org/D117537