Update devel/flang to latest github revision to chase their work in progress. While there include two suggestions by Steve Kargl in the flang wrapper script (add flang's include directory by default, add libompstub by default). Add a TESTS option that enables flang's internal unit tests (request on freebsd-fortran@). The last does not seem to be doing much in upstream yet.
There is still a problem when trying to compile statically. Also, OpenMP code does compile w/ -fopenmp -L/usr/local/lib but does not execute in parallel yet.