Fix f_check detection of LLVM 21 flang

[bartoldeman]

The check for GCC is confused by the GNU-stack in

	.file	"FIRModule"
	.text
	.globl	zhoge_
	.p2align	4
	.type	zhoge_,@function
zhoge_:
	xorps	%xmm0, %xmm0
	xorps	%xmm1, %xmm1
	retq
.Lfunc_end0:
	.size	zhoge_, .Lfunc_end0-zhoge_

	.ident	"flang version 21.1.5"
	.section	".note.GNU-stack","",@progbits

And displays:

./f_check: line 102: [: 	: integer expression expected

Since it expects a string with GCC anyway, better to only match GCC and not GNU.

[martin-frbg]

ISTR there is/was a reason for matching GNU in addition to GCC - probably earlier versions of gfortran not using GCC before the CC became associated with "compiler collection"

[bartoldeman]

If I look in the history it must have been lost in translation from perl to bash, as the perl code did:

} elsif ($data =~ /GNU/ || $data =~ /GCC/ ) {
            $data =~ s/\(+.*?\)+//g;
	    $data =~ /(\d+)\.(\d+).(\d+)/;
	    $major = $1;
	    $minor = $2;
	    if ($major >= 4) {
		$vendor = GFORTRAN;
		$openmp = "-fopenmp";

so there was no GCC in the $data setting regexps here unlike in the shell script.

[bartoldeman]

the oldest gfortran I have on hand has this:

	.file	"ftest.f"
	.text
	.p2align 4,,15
	.globl	zhoge_
	.type	zhoge_, @function
zhoge_:
.LFB0:
	.cfi_startproc
	xorpd	%xmm1, %xmm1
	movapd	%xmm1, %xmm0
	ret
	.cfi_endproc
.LFE0:
	.size	zhoge_, .-zhoge_
	.ident	"GCC: (GNU) 4.8.5"
	.section	.note.GNU-stack,"",@progbits

That's a 10 year old compiler, not sure if OpenBLAS still supports that?