LLVM Flang Build error in unit test

[mathomp4]

After using @scivision 's nice "build LLVM Flang" script to build LLVM Flang on bucy, the usual build test of GFE failed.

Steps to reproduce:

ml comp/llvm-flang/2024-05-06 mpi/openmpi/5.0.2/llvm-flang-2024-05-06

cmake -B build-Flang-Debug -S . --install-prefix=$(pwd)/install-Flang-Debug -DSKIP_OPENMP=ON -DENABLE_TESTS=ON -DCMAKE_BUILD_TYPE=Debug
cmake --build build-Flang-Debug --target install

cmake -B build-Flang-Debug -S . --install-prefix=$(pwd)/install-Flang-Debug -DSKIP_OPENMP=ON -DENABLE_TESTS=ON -DCMAKE_BUILD_TYPE=Debug
cmake --build build-Flang-Debug --target install

This is our usual two-step process as the first build builds pFUnit and the second build then sees pFUnit to build the unit tests.

When you do so you get a couple types of failures. Many of the first type, and a couple of the second:

[ 70%] Building Fortran object fArgParse/tests/CMakeFiles/fargparse_tests.dir/Test_ArgParser.F90.o
error: Semantic errors in /home/mathomp4/GFE-Flang/GFE/build-Flang-Debug/fArgParse/tests/Test_ArgParser.F90
/home/mathomp4/GFE-Flang/GFE/build-Flang-Debug/fArgParse/tests/Test_ArgParser.F90:25:17: error: No specific function of generic 'parse_args' matches the actual arguments
        options = p%parse_args(arguments)
                  ^^^^^^^^^^^^^^^^^^^^^^^
...
/home/mathomp4/GFE-Flang/GFE/fArgParse/tests/Test_ArgParser.pf:629:7: error: No specific subroutine of generic 'cast' matches the actual arguments
        call cast(options%at('potential'), p_vals)
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
...