undefine OFFSET in testsuite/gcc.dg/vect/tree-vect.h

2019-12-20  Olivier Hainque  <hainque@adacore.com>

	* gcc.dg/vect/tree-vect.h: #undef OFFSET.

From-SVN: r279797

gcc/testsuite/gcc.dg/vect/tree-vect.h

@@ -85,3 +85,9 @@ check_vect (void)
 #else
 #  define VECTOR_BITS 128
 #endif
+
+/* Which most of our tests are going to #define for internal use, and
+   which might be exposed by system headers related to signal.h on some
+   targets, notably VxWorks.  */
+#undef OFFSET
+