ga doesn't build with flang, doesn't respect F77/FC/CC/CXX/MPICC/MPICXX

[yurivict]

I'm trying to build with flang, the clang-based fortran compiler. It should use only clang-based toolchain.

However, it still uses gfortran6/gcc6:

...
configure:                    F77=mpif90
configure:          unwrapped F77=gfortran6
configure:                 FFLAGS= -O
configure:              FFLAG_INT=-fdefault-integer-8
configure:      FFLAG_NO_LOOP_OPT=-fno-aggressive-loop-optimizations
configure:                GA_FOPT=
configure:                     CC=mpicc
configure:           unwrapped CC=gcc6
configure:                 CFLAGS=-O2 -pipe -fno-omit-frame-pointer  -fstack-protector -fno-strict-aliasing
...

[yurivict]

Sorry, I was wrong...