testsuite: Use noinline in gcc.dg/simulate-thread/simulate-thread.h

testsuite: Use noinline in gcc.dg/simulate-thread/simulate-thread.h

Among the changes of test results with a -std=gnu23 default were two
tests changing from PASS to UNSUPPORTED:

UNSUPPORTED: gcc.dg/simulate-thread/speculative-store.c   -O2 -g  thread simulation test
UNSUPPORTED: gcc.dg/simulate-thread/speculative-store.c   -O3 -g  thread simulation test

It appears that functions defined with () becoming prototyped affects
inlining, and changing the code to use (void) allows UNSUPPORTED
results to be reproduced with -std=gnu17.  Add __attribute__
((noinline)) on one more function to avoid the UNSUPPORTED results;
some of the tests in this directory already have such an attribute on
some functions.

Tested for x86_64-pc-linux-gnu.

	* gcc.dg/simulate-thread/simulate-thread.h
	(simulate_thread_wrapper_final_verify): Mark noinline.