Do not force gcc options on non-gcc compilers
Do not force gcc options on non-gcc compilers

fixes compile failure with pgi 18.10 as reported on OpenBLAS-users
xianyi/OpenBLAS,xianyi/OpenBLAS,xianyi/OpenBLAS,xianyi/OpenBLAS,xianyi/OpenBLAS,xianyi/OpenBLAS,xianyi/OpenBLAS,xianyi/OpenBLAS