Quick fix of debugging option for mk1mf.pl.

util/mk1mf.pl was relying on the platform having the 'debug-' prefix
for doing a debug build.  Since the setup of targets has changed, this
is no longer true.  However, it can look for '--debug' in the command
line options.
Reviewed-by: NRich Salz <rsalz@openssl.org>

util/mk1mf.pl

@@ -83,8 +83,6 @@ while(<IN>) {
 }
 close(IN);
 
-$debug = 1 if $mf_platform =~ /^debug-/;
-
 if ($mf_fipscanisterinternal eq "y") {
 	$fips = 1;
 	$fipscanisterbuild = 1;
@@ -1401,6 +1399,7 @@ sub read_options
 		"rsaref" => 0,
 		"gcc" => \$gcc,
 		"debug" => \$debug,
+		"--debug" => \$debug,
 		"profile" => \$profile,
 		"shlib" => \$shlib,
 		"dll" => \$shlib,