Makefile.in: empty comment

* Makefile.in (mjit_config.h): add an empty comment if no content,
  to tell the empty content explicitly.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@62502 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

Makefile.in

@@ -546,7 +546,7 @@ mjit_config.h:
 	@{ \
 	quote() { \
 	    printf "#define $$1"; shift; \
-	    printf ''$${1+' "%s"'$$sep} "$$@"; \
+	    printf ''$${1+' "%s"'$$sep} $${1+"$$@"} $${1-" /**/"}; \
 	    echo; \
 	}; \
 	test "$(Q)" = @ || set -x; \