Fix our fortify tests for global -Werror.

If anyone has a better way of doing this it would be welcome...

Bug: http://b/26936282
Change-Id: I796896866327b4b5b5ee4ec36994fb320993f85d
diff --git a/tests/file-check-cxx b/tests/file-check-cxx
index 4018265..d3bc5f7 100755
--- a/tests/file-check-cxx
+++ b/tests/file-check-cxx
@@ -5,7 +5,7 @@
 shift 3
 SOURCE=$(echo "$@" | grep -oP '\S+\.cpp\b')
 OBJ=$(echo "$@" | grep -oP '\S+\.o\b')
-$CXX "$@" 2>&1 | $FILECHECK -check-prefix=$PREFIX $SOURCE
+$CXX "$@" -Wno-error 2>&1 | $FILECHECK -check-prefix=$PREFIX $SOURCE
 if [ "$?" -eq 0 ]; then
   touch $OBJ
 else