main/postmarketos-base: add dummy post-upgrade (MR 1964)

Add post-upgrade file with a warning, so we don't symlink it to the
post-install script.
[ci:skip-vercheck]: no need to rebuild the package

Related: build.postmarketos.org#85

main/postmarketos-base/APKBUILD

@@ -21,7 +21,7 @@ depends="
 	util-linux
 	wpa_supplicant
 	"
-install="$pkgname.post-install $pkgname.pre-upgrade"
+install="$pkgname.post-install $pkgname.pre-upgrade $pkgname.post-upgrade"
 triggers="$pkgname.trigger=/etc"
 subpackages="
 	$pkgname-elogind

main/postmarketos-base/postmarketos-base.post-upgrade

+#!/bin/sh
+# WARNING: do not symlink this file to postmarketos-base.post-install!
+# Otherwise it will enable services, as listed in that file. And we don't want
+# this to happen during upgrade, especially not automatically enabling the sshd
+# service! (build.postmarketos.org#85)