Don't use a default for --with-zlib-lib on Windows with option 'zlib'

To begin with, the default should have been the import library, not
the DLL itself.  However, we don't know what directory it's installed
in either way, so we may as well demand the full path from the user

Reviewed-by: Matt Caswell <matt@openssl.org>

Configurations/00-base-templates.conf

@@ -80,7 +80,7 @@
             sub {
                 unless ($disabled{zlib}) {
                     if (defined($disabled{"zlib-dynamic"})) {
-                        return $withargs{zlib_lib} || "zlib1.lib";
+                        return $withargs{zlib_lib};
                     }
                 }
                 return (); },