Support multiple build variants, add ARM variant

src/main.c

@@ -1,7 +1,10 @@
 #include <stdio.h>
 #include <stdlib.h>
+
+#ifndef NO_READLINE
 #include <readline/readline.h>
 #include <readline/history.h>
+#endif
 
 #include "uclisp.h"
 
@@ -71,14 +74,18 @@ int main(int argc, const char **argv) {
 
     if (argc < 2) {
         while (1) {
-            char *line = readline("> ");
+            char *line = NULL;
+#ifndef NO_READLINE
+            line = readline("> ");
             if (line == NULL) {
                 break;
             }
             if (strlen(line) > 0) {
                 add_history(line);
             }
-
+#else
+            // TODO
+#endif
             struct ucl_object *sexp = ucl_parse(line);
             struct ucl_object *result = NULL;
             if (sexp->type == UCL_TYPE_ERROR) {