Don't set package-group as a PACKAGE_TYPE.

Since package groups can theoretically now be installed as
native:package-group as well, make PACKAGE_TYPE only ever have a value
of "target" or "native". For a native install it's important we
transform the names of all dependencies to have the native: prefix.

It doesn't matter if we uselessly set PACKAGE_INSTALL_DIR and
PACKAGE_BUILD_DIR for a package group anyway, since they're not used
anyway.

chocpkg/chocpkg

@@ -111,8 +111,6 @@ configure_for_package() {
             # necessarily native as well.
             DEPENDENCIES=$(dependencies_for_native)
             ;;
-        package-group)
-            ;;
         *)
             error_exit "Unknown package type $PACKAGE_TYPE"
             ;;

chocpkg/modules/package_group.sh

@@ -1,6 +1,5 @@
 
 package_group::init() {
-    PACKAGE_TYPE=package-group
     dependencies "$@"
 }