This patch adds the lowering for the RTLModuleFlagsAttr to LLVM-IR,
which lowers each individual argument of the attribute to globals. As well
as the application of it by flags in the frontend which have been activated
for flang fc1.
This patch enables the RTL flags below (and any equals or inverse variants) for Flang that exist in Clang:
-fopenmp-target-debug
-fopenmp-assume-threads-oversubscription
-fopenmp-assume-teams-oversubscription
-fopenmp-assume-no-nested-parallelism
-fopenmp-assume-no-thread-state
Then generates an OpenMP MLIR Dialect RTLModuleFlagsAttr to hold this information and proliferate it down to the translation to LLVM-IR that occurs in OpenMPToLLVMIRTranslation, allowing use of the OpenMPIRBuilder.