Compiler support and recognition

[awvwgk]

Came up in #220.

At some point we might have to determine which compiler is used with fpm, therefore I tried to collect some information on the various Fortran compilers around. I only have first hand access to a fraction of them, so most of these information are second hand from HPC documentations or build systems.

Feel free to correct or add information to this table. Alternatively, we could move this table to the wiki.

vendor	Fortran compiler	C compiler	Module output directory	Module include directory	OpenMP	Free for OSS
Gnu	gfortran	gcc	-J	-I	-fopenmp	:heavy_check_mark:
Intel	ifort	icc	-module	-I	-qopenmp	:heavy_check_mark:
Intel (Windows)	ifort	icc	/module:path	/I	/Qopenmp	:heavy_check_mark:
Intel oneAPI	ifx	icx	-module	-I	-qopenmp	:heavy_check_mark:
PGI	pgfortran	pgcc	-module	-I	-mp	:heavy_check_mark:
NVIDIA	nvfortran	nvc	-module	-I	-mp	:heavy_check_mark:
LLVM flang	flang	clang	-module	-I	-mp	:heavy_check_mark:
LFortran	lfortran	---	?	?	?	:heavy_check_mark:
Lahey/Futjitsu	lfc	?	-M	-I	-openmp	?
NAG	nagfor	?	-mdir	-I	-openmp	:x:
Cray	crayftn	craycc	-J	-I	-homp	?
IBM	xlf90	?	-qmoddir	-I	-qsmp	:heavy_check_mark:
Oracle/Sun	?	?	-moddir=	-M	-xopenmp	?
Silverfrost FTN95	ftn95	?	?	/MOD_PATH	?	?
Elbrus	?	lcc	-J	-I	-fopenmp	?
Hewlett Packard	?	?	?	?	?	discontinued
Watcom	?	?	?	?	?	discontinued
PathScale	?	?	-module	-I	-mp	discontinued
G95	?	?	-fmod=	-I	-fopenmp	discontinued
Open64	?	?	-module	-I	-mp	discontinued
Unisys	?	?	?	?	?	discontinued

For now it might be sufficient to only support GCC, since we only guarantee that fpm works when compiled with GCC right now.

First class compiler support requires access to the compiler to allow testing in a CI environment, some of the commercial compilers have free versions for open source developers available.