Upstream backport.
Get rid of PKG_RELEASE as it's irrelevant to tools.
Signed-off-by: Rosen Penev <rosenp@gmail.com>
(cherry picked from commit 253d777c96)
Link: https://github.com/openwrt/openwrt/pull/15898
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>