Revert "deletion of clang_cflags & clang_asflags from Soong"

Revert submission 2154033-delete clang_cflags clang_asflags

Reason for revert: Broke build on git_tm-dev-plus-aosp and downstream branches

Reverted Changes:
I5c499a37e:Default BuildBrokenClangCFlags &  BuildBrokenClang...
Ic1d90b72d:deletion of clang_cflags & clang_asflags from Soon...

Change-Id: Ic55dd85a824cf1a543249e0b00072b8c08a475b8