Ports: Build ports only once when running build_all.sh

Previously we'd end up building some ports multiple times, e.g.
as a dependency for another port. This changes the build_all.sh
script so that it builds ports only once.

Ports/build_all.sh

@@ -26,11 +26,31 @@ case "$2" in
 esac
 
 some_failed=false
+built_ports=""
 
 for file in *; do
     if [ -d $file ]; then
         pushd $file > /dev/null
             port=$(basename $file)
+            port_built=0
+            for built_port in $built_ports; do
+                if [ "$built_port" = "$port" ]; then
+                    port_built=1
+                    break
+                fi
+            done
+            if [ $port_built -eq 1 ]; then
+                echo "Already built $port as a dependency."
+                popd > /dev/null
+                continue
+            fi
+            if ! [ -f package.sh ]; then
+                echo "ERROR: Skipping $port because its package.sh script is missing."
+                popd > /dev/null
+                continue
+            fi
+            built_ports="$built_ports $port $(./package.sh showdepends) "
+
             if [ "$clean" == true ]; then
                 if [ "$verbose" == true ]; then
                     ./package.sh clean_all