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.

[josemonsalve2]

https://www.gnu.org/software/make/manual/html_node/File-Name-Functions.html

Using notdir in the comparison will be the solution.

[josemonsalve2]

And for postfix probably use this:
https://www.gnu.org/software/make/manual/html_node/Text-Functions.html