aarch64 builder broke with:
- Supported architectures for crt: aarch64
CMake Error at compiler-rt/cmake/config-ix.cmake:244 (message):
Unsupported architecture: x86_64
Call Stack (most recent call first):
compiler-rt/cmake/config-ix.cmake:280 (get_target_flags_for_arch) compiler-rt/test/metadata/CMakeLists.txt:7 (get_test_cc_for_arch)
- Configuring incomplete, errors occurred!
https://lab.llvm.org/buildbot/#/builders/223/builds/11423
Restrict the tests to x86_64 only.