Ports: Do not allow clean* to be overridden

There were only two packages making use of this functionality, but it
seems more sensible to have a fixed implementation for the cleaning of
ports - especially now they delete the entire build directory and/or
dist files.

Ports/.port_include.sh

@@ -440,10 +440,10 @@ func_defined install || install() {
 func_defined post_install || post_install() {
     echo
 }
-func_defined clean || clean() {
+clean() {
     rm -rf "${PORT_BUILD_DIR}"
 }
-func_defined clean_dist || clean_dist() {
+clean_dist() {
     OLDIFS=$IFS
     IFS=$'\n'
     for f in $files; do
@@ -452,7 +452,7 @@ func_defined clean_dist || clean_dist() {
         rm -f "${PORT_META_DIR}/${filename}"
     done
 }
-func_defined clean_all || clean_all() {
+clean_all() {
     clean
     clean_dist
 }

Ports/qt6-qtbase/package.sh

@@ -57,7 +57,3 @@ install() {
     echo "The development of the Qt Serenity platform plugin is happening here. Fixes for things like input handling, window management and theme integration should go here:"
     echo -e "\t" "https://github.com/SerenityPorts/QSerenityPlatform"
 }
-
-clean() {
-    run ninja clean
-}

Ports/qt6-serenity/package.sh

@@ -37,7 +37,3 @@ build() {
 install() {
     run ninja install
 }
-
-clean() {
-    run ninja clean
-}