mozjs17: fix gcc7 build

srcpkgs/mozjs17/patches/gcc7-empty_string_comparison.patch

@@ -0,0 +1,11 @@
+--- js/src/shell/jsoptparse.cpp	2013-02-11 23:33:23.000000000 +0100
++++ js/src/shell/jsoptparse.cpp	2017-05-09 16:05:19.657666914 +0200
+@@ -243,7 +243,7 @@
+     char *eq = strchr(argv[*i], '=');
+     if (eq) {
+         *value = eq + 1;
+-        if (value[0] == '\0')
++        if (*value[0] == '\0')
+             return error("A value is required for option %.*s", eq - argv[*i], argv[*i]);
+         return Okay;
+     }