[VxWorks, committed] Fix gcc.dg/cpp/assert4.c failure

[Richard Sandiford]

VxWorks declares itself to be a unix target, so I've updated
gcc.dg/cpp/assert4.c accordingly.  Tested on i586-wrs-vxworks
and x86_64-linux-gnu.  Applied to mainline as obvious.

Richard


gcc/testsuite/
	* gcc.dg/cpp/assert4.c: Treat VxWorks as a unix target.

Index: gcc/testsuite/gcc.dg/cpp/assert4.c
===================================================================
--- gcc/testsuite/gcc.dg/cpp/assert4.c	(revision 122924)
+++ gcc/testsuite/gcc.dg/cpp/assert4.c	(working copy)
@@ -78,7 +78,8 @@
 # error
 #endif
 
-#if ( defined __unix__ && !defined __CYGWIN__ ) || defined _AIX
+#if ( defined __unix__ && !defined __CYGWIN__ ) || defined _AIX \
+    || defined __vxworks
 # if !#system(unix)
 #  error
 # endif