Makefile does not work with absolute compiler path in CC, CXX, and FC variables

[naromero77]

Describe the bug If CC, CXX, or FC include the absolute compiler path. The build system gets very confused. Here is the work around @josemonsalve2 came up with for my Linux desktop. I have GCC-9 with the NVidia backend installed via Spack.

PATH=/scratch/naromero/opt/spack/linux-ubuntu18.04-westmere/gcc-8.3.0/gcc-9.2.0-oavx2juw3k6od5vagdvtshcwrgclcmqv/bin/:$PATH make CC=gcc CXX=g++ FC=gfortran SOURCES=offloading_success.c VERBOSE=1 VERBOSE_TESTS=1 LOG=1 LOG_ALL=1 all

But without the $PATH, GCC is not properly detected.

Test that it applies to All tests

To Reproduce See above line.

Expected behavior Test suite compiles and runs.

Compiler GCC 9 with NVidia backend compiled via Spack

Accelerator hardware NVidia GPU card.