Enable clang compilation with libc but not linker.

Clang is still disabled for x86 and x86_64 long double code,
for x86_64 special assembly instruction, and the linker module.

BUG: 17163651
BUG: 17302991
BUG: 17403674

(cherry picked from commit b58db8b083ce41798a5310616e4f20885cec611f)

Change-Id: I916c05056d37a9c287b0a5ae3b1a209d98c8f70e
2 files changed