[testsuite] [analyzer] require fork where used

Mark tests that fail due to the lack of fork, as in vxworks kernel
mode, as requiring fork.


for  gcc/testsuite/ChangeLog

	* gcc.dg/analyzer/pipe-glibc.c: Require fork.
	* gcc.dg/analyzer/pipe-manpages.c: Likewise.

gcc/testsuite/gcc.dg/analyzer/pipe-glibc.c

-/* Example of pipe usage from glibc manual.  */
-
 /* { dg-skip-if "" { "avr-*-*" } } */
+/* { dg-require-fork "" } */
+
+/* Example of pipe usage from glibc manual.  */
 
 #include <sys/types.h>
 #include <unistd.h>

gcc/testsuite/gcc.dg/analyzer/pipe-manpages.c

+/* { dg-require-fork "" } */
+
 /* Example of "pipe" from release 5.13 of the Linux man-pages project.
 
 Copyright (C) 2005, 2008, Michael Kerrisk <mtk.manpages@gmail.com>