The unitest and test cases are platform dependent (x86_64)
causing failures in:
https://lab.llvm.org/buildbot/#/builders/245/builds/146
https://lab.llvm.org/buildbot/#/builders/188/builds/21397
No available targets are compatible with triple "x86_64-unknown-unknown".
Added:
- ';REQUIRES: x86-registered-target' to the LIT tests.
- Code to check if the target 'Triple::x86_64' is supported to the unittest case.