* Adds a config/clang-fflags options file to support Flang
* Corrects missing "-Wl," from linker options in the libtool wrappers
when using Flang, the MPI Fortran compiler wrappers, and building
the shared library. This would often result in unrecognized options
like -soname.
* Enable -nomp w/ Flang to avoid linking to the OpenMPI library.
CMake can build the parallel, shared library w/ Fortran using AOCC
and Flang, so no changes were needed for that build system.
Fixes GitHub issues #3439, #1588, #366, #280
