[compiler-rt] Move -fno-omit-frame-pointer check to common config-ix

9ee64c37 has started using
COMPILER_RT_HAS_OMIT_FRAME_POINTER_FLAG inside scudo.  However,
the relevant CMake check was performed in builtin-config-ix.cmake,
so the definition was missing when builtins were not built.  Move
the check to config-ix.cmake, so that it runs unconditionally of
the components being built.

Fixes PR#51847

Differential Revision: https://reviews.llvm.org/D109812