NVCC Specific Compiler Flag Propagates to Downstream Fortran Compiler

[Fuad-HH]

I was using PCMS (with MeshFields) for XGC and was getting the following error.

[ 50%] Building Fortran object CMakeFiles/libxgc-es-cpp-gpu.dir/XGC_core/one_d_cub_mod.F90.o
gfortran: error: unrecognized command-line option '--expt-relaxed-constexpr'
gfortran: error: unrecognized command-line option '--expt-relaxed-constexpr'
gfortran: error: unrecognized command-line option '--expt-relaxed-constexpr'
gfortran: error: unrecognized command-line option '--expt-relaxed-constexpr'
gfortran: error: unrecognized command-line option '--expt-relaxed-constexpr'
gfortran: error: unrecognized command-line option '--expt-relaxed-constexpr'
gfortran: error: unrecognized command-line option '--expt-extended-lambda'
gmake[3]: *** [CMakeFiles/libxgc-es-cpp-gpu.dir/build.make:1520: CMakeFiles/libxgc-es-cpp-gpu.dir/XGC_core/cpp/domain_decomposition/partition_intersect.F90.o] Error 1
gmake[3]: *** Waiting for unfinished jobs....
gfortran: error: unrecognized command-line option '--expt-extended-lambda'

This is coming from manually specified compiler flag here:

meshFields/CMakeLists.txt

Lines 61 to 63 in b1482bb

	if(Kokkos_ENABLE_CUDA)
	target_compile_options(meshfields INTERFACE "--expt-relaxed-constexpr")
	endif()

I think this can be fixed with a CXX language guard. Here's an example in StackOverflow.