Add explicit "./" in mkfiles.pl's require statements.

I've just tried for the first time to run mkfiles.pl on a system where
plain 'require "sbcsgen.pl"' does not search the cwd by default.

mkfiles.pl

@@ -47,8 +47,8 @@ open IN, "Recipe" or do {
 # HACK: One of the source files in `charset' is auto-generated by
 # sbcsgen.pl, and licence.h is likewise generated by licence.pl. We
 # need to generate those _now_, before attempting dependency analysis.
-eval 'chdir "charset"; require "sbcsgen.pl"; chdir ".."; select STDOUT;';
-eval 'require "licence.pl"; select STDOUT;';
+eval 'chdir "charset"; require "./sbcsgen.pl"; chdir ".."; select STDOUT;';
+eval 'require "./licence.pl"; select STDOUT;';
 
 @srcdirs = ("./");