provide option to deviate from compiler used to build perl

[oodler577]

I'd like to be able to compile openmp stuff using a different compiler that the one used to build perl; specifically the case where perl is compiled with gcc and I want to compile Inline OpenMP with icc - and the other way around. I am certain this is feasible, just don't know atm how feasible.

Example,

use Inline (
    C  => 'DATA',
    with         => q{Alien::OpenMP},
    compiler => ICC,
);

my $oenv = OpenMP::Environment->new;

for my $i (qw/1 2 4 8 16 32 64 128/) {
    $oenv->omp_num_threads($i);
    test
}
__DATA__
__C__
#include <omp.h>
#include <stdio.h>
#include <p5-inline-openmp-utils.h>

void test(void) {
  #pragma omp parallel
  {
    if (0 == omp_get_thread_num())
      printf("'%d' should be '%d'\n", omp_get_num_threads(), num_threads); 
  }
}```

[zmughal]

There is a hack used in the PDL CI workflow that gets ExtUtils::MakeMaker to use clang to build PDL's C code with a Linux perl that was built with gcc, so it is possible as long as certain config values can be changed:

https://github.com/PDLPorters/pdl/blob/2.061/.github/workflows/ci.yml#L67-L74

edit: already mentioned this previously at #6 (comment)

[oodler577]

I would like to do this, and it would be helpful on environments (e.g., HPC clusters) that use perl based on gcc but provide access to commercial compilers. So that one may specify with a perl build using gcc that they want to use a different suite of compilers for their OpenMP work (e.g., Intel, Portland Group, NAG, etc).

[oodler577]

This should be the next capability, I'll start working on it. I happen to have access to various HPC environments and commercial compilers, and it'll give me a reason to actually use this module on them. And that might drive some additional ideas - which will hopefully lead to a real case for an Inline::C::OpenMP type module.

[oodler577]

picking this up, targeting some time before TPC