prefer qmake6 when available (#315)

Author: jgcodes2020

qttypes/build.rs

@@ -43,8 +43,8 @@ fn qmake_query(var: &str) -> String {
         Err(_env_var_err) => {
             (|| {
                 // Some Linux distributions (Fedora, Arch) rename qmake to qmake-qt5.
-                // qmake6 is somehow an official alias
-                for qmake in &["qmake", "qmake6", "qmake-qt5"] {
+                // qmake6 is an official alias that generally always points to the Qt6 version.
+                for qmake in &["qmake6", "qmake", "qmake-qt5"] {
                     match Command::new(qmake).args(&["-query", var]).output() {
                         Err(err) if err.kind() == std::io::ErrorKind::NotFound => continue,
                         x => return x,