--- /dev/null
+# tl_CHECK_TOOL_PREFIX will work _BEFORE_ AC_CANONICAL_HOST, etc., has been
+# called. It should be called again after these have been called.
+#
+# Basically we want to check if the host alias specified by the user is
+# different from the build alias. The rules work like this:-
+#
+# If host is not specified, it defaults to NONOPT
+# If build is not specified, it defaults to NONOPT
+# If nonopt is not specified, we guess all other values
+