nonclangable: Use libgcc for unwinder as well when using for builtins
nonclangable: Use libgcc for unwinder as well when using for builtins

clang 13 does not like to mix rtlib and unwindlib when using libgcc

Fixes
clang-13: error: --rtlib=libgcc requires --unwindlib=libgcc

secondly compiler-rt does not havw 128 bit ( tf ) functions
on x86 so fallback to libgcc for those

use libatomic for x86 since 64bit atomics are not in compiler-rt

Signed-off-by: Khem Raj <729d64b6f67515e258459a5f6d20ec88b2caf8df@gmail.com>

kraj/meta-clang,kraj/meta-clang,kraj/meta-clang