libgomp: Make libgomp.c/declare-variant-1.c test x86 specific

libgomp: Make libgomp.c/declare-variant-1.c test x86 specific

As written earlier, this test was written with the x86 specifics in mind
and adding dg-final directives for it for other arches makes it unreadable.
If a declare variant call can be resolved in gimple already as in the
aarch64 or gcn cases, it can be done in gcc.dg/gomp/ and I believe we have
tests like that already, the point of the test is that it is not known
during gimplification time which exact call should be chosen as it depends
on which declare simd clone it will be in.

2023-12-18  Jakub Jelinek  <jakub@redhat.com>

	* testsuite/libgomp.c/declare-variant-1.c: Restrict the test to x86,
	drop because of that unneeded target selector from other directives
	and remove the aarch64 specific ones.