[PATCH] XFAIL ptrace test on arm

[Greg Fitzgerald]

> Shouldn't this be called COMPILER_RT_TEST_TARGET_TRIPLE instead?

Would you prefer I add '_TEST' here?  If *_COMPILER_ID==Clang, it's safe to use this value for the -target flag as well.  This variable could be a convenient way to mix and match GCC and Clang.  We could remove -target from CMAKE_C_FLAGS and COMPILER_RT_TEST_CFLAGS and then automatically add it in whenever *_COMPILER_ID==Clang.

http://reviews.llvm.org/D3855