Custom make flags in ReFrame

[lucamar]

It could be useful to customize make flags that ReFrame uses when building. For instance, if a modulefile sets mpif90=$MPIF90, then ReFrame creates the following make line:

make -j CC='mpicc' CXX='mpicxx' FC='$MPIF90' NVCC='nvcc' FCFLAGS='-O2 -acc -ta=tesla,cc35' LDFLAGS='-acc -ta:tesla:cc35 -lstdc++' NVCC_FLAGS="-arch=compute_37"

The command would fail in this case:

PIF90 compute_cuda.o openacc_cuda_mpi_cppstd.o std_cpp_call.o -o openacc_cuda_mpi_cppstd -acc -ta:tesla:cc35 -lstdc++
make: PIF90: Command not found