Apply compiler-rt fix for building with earlier versions of clang

Apply compiler-rt fix for building with earlier versions of clang

Merge commit 18efa420da5f from llvm git (by Brooks Davis)

  compiler-rt: Allow build without __c11_atomic_fetch_nand

  Don't build atomic fetch nand libcall functions when the required
  compiler builtin isn't available. Without this compiler-rt can't be
  built with LLVM 13 or earlier.

  Not building the libcall functions isn't optimal, but aligns with the
  usecase in FreeBSD where compiler-rt from LLVM 14 is built with an LLVM
  13 clang and no LLVM 14 clang is built.

  Reviewed By:	  efriedma

  Differential Revision:  https://reviews.llvm.org/D126710

MFC after:	3 days