rest-api: add config dir parametrable.

src/3P/uhttpd/main.c

@@ -148,6 +148,9 @@ static int usage(const char *name)
 		"	-l string       URL prefix for Lua handler, default is '/lua'\n"
 		"	-L file         Lua handler script, omit to disable Lua\n"
 #endif
+#ifdef HAVE_REST_API_PLUGING
+		"	-U directory    Specify the config root path\n"
+#endif
 #ifdef HAVE_UBUS
 		"	-u string       URL prefix for UBUS via JSON-RPC handler\n"
 		"	-U file         Override ubus socket path\n"
@@ -441,11 +444,16 @@ int main(int argc, char **argv)
 #else
 		case 'a':
 		case 'u':
-		case 'U':
+		//case 'U':
 		case 'X':
 			fprintf(stderr, "uhttpd: UBUS support not compiled, "
 			                "ignoring -%c\n", ch);
 			break;
+#endif
+#ifdef HAVE_REST_API_PLUGING
+		case 'U':
+			conf.ubus_prefix = optarg;
+			break;
 #endif
 		default:
 			return usage(argv[0]);