testsuite/gcc.dg/memcmp-1.c: Cut down a factor of 7 for simulators

Running tests in parallel on my 4.5y+ old laptop made this
test time out: the test itself runs in 9m20s, the timeout
being 10 minutes with the 2x factor.  That's a bit too close.

This commit does to the base test a similar change as was
done for gcc.dg/torture/inline-mem-cpy-1.c in commit
r14-8188-g6eca0d23b7ea84; or IOW cut it down a factor of 7
(r14-8188 was by a factor of 11).

	* gcc.dg/memcmp-1.c: Pass -DRUN_FRACTION=7 when testing in a simulator.

gcc/testsuite/gcc.dg/memcmp-1.c

@@ -2,6 +2,7 @@
 /* { dg-do run } */
 /* { dg-options "-O2" } */
 /* { dg-require-effective-target ptr32plus } */
+/* { dg-additional-options "-DRUN_FRACTION=7" { target simulator } } */
 /* { dg-timeout-factor 2 } */
 
 #include <stdio.h>