This patch turns on support for CR bit accesses for Power8 and above. The reason why CR bits are turned
on as the default for Power8 and above is that because later architectures make use of builtins and
instructions that require CR bit accesses (such as the use of setbc in the vector string isolate predicate
and bcd builtins on Power10).
This patch also adds the clang portion to allow for turning on CR bits in the front end if the user so desires to.
If we set the +crbits by the arch name, do we still need the customization (Turn on crbits for O2 and above) in computeFSAdditions()?