[OpenMP][test] Regression tests for OpenMPIRBuilder.
Categorize libomp regression tests according to whether they currently work with `-fopenmp-enable-irbuilder`. Tests marked with `XFAIL` are reliably failing. Tests with `UNSUPPORTED` fail or succeed occasionally. Add some additional tests that currently fail using the OpenMPIRBuilder.
Differential Revision: https://reviews.llvm.org/D114501
