Don't start Configure.pl without ExtUtils::Command

Not all distros include this module, but it is needed to run the Makefile.
If a user would try and install Rakudo Star and they don't have the module,
this would obscure the missing module and they likely would not know why
the Rakudo Star compilation/installation was failing.

`use` the module in Configure.pl so the user immediately knows they must
install this module if they do not have it.

Configure.pl

@@ -18,8 +18,10 @@
 my $uclang = uc $lang;
 my $win    = $^O eq 'MSWin32';
 my $slash  = $win ? '\\' : '/';
-
-
+# We don't use ExtUtils::Command in Configure.pl, but it is used in the Makefile
+# Try `use`ing it here so users know if they need to install this module
+# (not included with *every* Perl installation)
+use ExtUtils::Command;
 MAIN: {
     if (-r 'config.default') {
         unshift @ARGV, shellwords(slurp('config.default'));