scripts/extract: use tar to copy to correct directory

also add support for custom tar opt, eg to exclude files
or directories when copying

This can be set eg with PKG_TAR_COPY_OPTS="--exclude=.git"

scripts/extract

@@ -70,6 +70,9 @@ case $PKG_SOURCE_NAME in
     zcat $FULL_SOURCE_PATH | patch -d $2 -p1
     ;;
   *)
-    cp -pPR $FULL_SOURCE_PATH $2
+    FULL_DEST_PATH="$2/$PKG_NAME-$PKG_VERSION"
+    mkdir $FULL_DEST_PATH
+    tar cf - -C $FULL_SOURCE_PATH $PKG_TAR_COPY_OPTS . | \
+      tar xf - -C $FULL_DEST_PATH
     ;;
 esac