perf tools: annotate asm_pure_loop.S

Annotate so it is built with non-executable stack.

Fixes: 8b97519 ("perf test: Add asm pureloop test tool")
Signed-off-by: Marcus Meissner <meissner@suse.de>
Reviewed-by: Leo Yan <leo.yan@arm.com>
Link: https://lore.kernel.org/r/20250323085410.23751-1-meissner@suse.de
Signed-off-by: Namhyung Kim <namhyung@kernel.org>

Author: msmeissn

tools/perf/tests/shell/coresight/asm_pure_loop/asm_pure_loop.S

@@ -26,3 +26,5 @@ skip:
 	mov	x0, #0
 	mov	x8, #93 // __NR_exit syscall
 	svc	#0
+
+.section .note.GNU-stack, "", @progbits