Add 'libgomp.c/alloc-ompx_host_mem_alloc-1.c'

Add 'libgomp.c/alloc-ompx_host_mem_alloc-1.c'

OpenMP 'ompx_host_mem_alloc' is available for host and nvptx offloading as of
og12 commit 84914e197d91a67b3d27db0e4c69a433462983a5
"openmp, nvptx: ompx_unified_shared_mem_alloc", and for GCN offloading as of
og12 commit c77c45a641fedc3fe770e909cc010fb1735bdbbd
"amdgcn, libgomp: low-latency allocator".

	libgomp/
	* testsuite/libgomp.c/alloc-ompx_host_mem_alloc-1.c: New.