Make "buildconf --force" more robust, per IRC chat. Not backported to 5.3 to avoid destabilization.

buildconf

@@ -32,7 +32,12 @@ if test "$dev" = "0" -a "$devok" = "0"; then
   echo "use buildconf --force to override this check."
   exit 1
 fi
- 
+
+if test "$devok" = "1"; then
+  echo "Removing configure caches"
+  rm -rf autom4te.cache config.cache
+fi
+
 rm -f generated_lists
 
 if test "$debug" = "yes"; then