[llvm] [Bazel] Define BUILTIN_THREAD_POINTER where appropriate on x86-64 linux (PR #74574)

[Fangrui Song via llvm-commits]

MaskRay wrote:

The CMake check was introduced in 822c31a0fe827a6f33601ad6b44eb2818350da36 and adjusted (`used`) in a54545ba6514802178cf7cf1c1dd9f7efbf3cde7. Perhaps we can also disable Bazel builds if GCC<=10 or Clang<=13 at another layer?
People who use this unofficial build system seem to use very new Clang or GCC.
(Also we don't have build bots for older compilers, so  they may not even work.)

https://github.com/llvm/llvm-project/pull/74574