Disable warnings on thread pool exhaustion in posixtest

posixtest.test_pthread_cond_broadcast_1_2 seems to trigger this.

Author: kleisauke

test/test_posixtest.py

@@ -188,7 +188,8 @@ def f(self):
             '-pthread',
             '-sEXIT_RUNTIME',
             '-sTOTAL_MEMORY=256mb',
-            '-sPTHREAD_POOL_SIZE=40']
+            '-sPTHREAD_POOL_SIZE=40',
+            '-sPTHREAD_POOL_SIZE_STRICT=0']
     if browser:
       self.btest_exit(testfile, args=args)
     else: