Missed a grep

Makefile.am

@@ -412,7 +412,7 @@ src/include/switch_version.h: src/include/switch_version.h.in .version $(libfree
 	@have_version=1 ; \
 	force=0 ; \
 	grep -- "@SWITCH_VERSION_REVISION@" src/include/switch_version.h.in > /dev/null  && have_version=0 ; \
-	test ! -f src/include/switch_version.h || grep "@SWITCH_VERSION_REVISION@" src/include/switch_version.h > /dev/null && force=1 ; \
+	test ! -f src/include/switch_version.h || grep -- "@SWITCH_VERSION_REVISION@" src/include/switch_version.h > /dev/null && force=1 ; \
 	if test $$have_version = 1 ; then \
 	  cat src/include/switch_version.h.in > src/include/switch_version.h ; \
 	  touch .version ; \