Require C++20 for building Stepmania.

src/CourseUtil.cpp

@@ -304,7 +304,7 @@ void CourseUtil::AutogenOniFromArtist( const RString &sArtistName, RString sArti
 	 * song set changes. */
 	{
 		RandomGen rng( GetHashForString( sArtistName ) + aSongs.size() );
-		random_shuffle( aSongs.begin(), aSongs.end(), rng );
+		shuffle( aSongs.begin(), aSongs.end(), rng );
 	}
 
 	// Only use up to four songs.