New 3.8 clang/llvm can compile TLS code now.
* For x86_64, still disable clang due to f128 bug.
* For b/25643775, arm and arm64, disable clang in unit tests.
* Fix thread_local_test.cpp to compile with clang and
limit gcc workaround only to arm and aarch64.
BUG: 25643775
Change-Id: Iecd006bf1fc417dbcce2c63343a59c4bf1fa77ea
This test should pass with gcc and fail with clang,
until clang/llvm supports emutls or Android linker supports
ELF TLS models.
BUG: 21082792
Change-Id: Id8c97da52c68ec230c7d26af703f6ed32d53a4fe