libgomp: Add gfx90c, 1036 and 1103 declare variant tests

libgomp: Add gfx90c, 1036 and 1103 declare variant tests

Recently -march=gfx{90c,1036,1103} support has been added, but corresponding
changes weren't done in the testsuite.

The following patch adds that.

Tested on x86_64-linux (with fiji and gfx1103 devices; had to use
OMP_DEFAULT_DEVICE=1 there, fiji doesn't really work due to LLVM dropping
support, but we still list those as offloading devices).

2024-05-02  Jakub Jelinek  <jakub@redhat.com>

	* testsuite/libgomp.c/declare-variant-4.h (gfx90c, gfx1036, gfx1103):
	New functions.
	(f): Add #pragma omp declare variant directives for those.
	* testsuite/libgomp.c/declare-variant-4-gfx90c.c: New test.
	* testsuite/libgomp.c/declare-variant-4-gfx1036.c: New test.
	* testsuite/libgomp.c/declare-variant-4-gfx1103.c: New test.