As Peter S. Mazinger has pointed out, the config system wants

some defaults.  So give it some empty defaults and let people
select their own options.

extra/Configs/Config.default

@@ -0,0 +1,2 @@
+# This file is empty to let people select their own
+# build options however they like....

extra/config/confdata.c

@@ -15,7 +15,7 @@
 
 const char conf_def_filename[] = ".config";
 
-const char conf_defname[] = "extra/Configs/Config.$TARGET_ARCH.default";
+const char conf_defname[] = "extra/Configs/Config.default";
 
 const char *conf_confnames[] = {
 	".config",