main/postmarketos-mkinitfs: trigger: add skip hint (MR 6325)

The recent optimization of not running "mkinitfs" during the trigger
script when running in pmbootstrap lead to unexpected behavior for some
use cases: testing initramfs changes and upgrading the initramfs in the
chroot (e.g. with pmbootstrap chroot --image). Let the user know that it
gets skipped and tell them how they can force building a new initramfs,
as discussed with Caleb.

[ci:skip-build]: already built successfully in CI

main/postmarketos-mkinitfs/APKBUILD

@@ -2,7 +2,7 @@
 # Co-Maintainer: Clayton Craft <clayton@craftyguy.net>
 pkgname=postmarketos-mkinitfs
 pkgver=2.6.1
-pkgrel=1
+pkgrel=2
 pkgdesc="Tool to generate initramfs images for postmarketOS"
 url="https://postmarketos.org"
 depends="

main/postmarketos-mkinitfs/postmarketos-mkinitfs.trigger

@@ -2,12 +2,19 @@
 # This script fails on error (-e). We don't want an error while generating the
 # initramfs to go unnoticed, it may lead to the device not booting anymore.
 
-# Conditionally run mkinitfs:
-# * Only invoke mkinitfs if the deviceinfo exists in the rootfs.
-# * Don't run mkinitfs inside "pmbootstrap install" with this trigger script,
-#   as it would trigger multiple times as the rootfs gets constructed, slowing
-#   down the process. Instead, pmbootstrap runs "mkinitfs" explicitly once at
-#   the end of "pmbootstrap install".
-if [ -f /usr/share/deviceinfo/deviceinfo ] && ! [ -f /in-pmbootstrap ]; then
-	/usr/sbin/mkinitfs
+if ! [ -f /usr/share/deviceinfo/deviceinfo ]; then
+	echo "mkinitfs: skipping (no deviceinfo file found)"
+	exit 0
 fi
+
+# Don't run mkinitfs inside "pmbootstrap install" with this trigger script, as
+# it would trigger multiple times as the rootfs gets constructed, slowing down
+# the process. Instead, pmbootstrap runs "mkinitfs" explicitly once at the end
+# of "pmbootstrap install".
+if [ -f /in-pmbootstrap ]; then
+	echo "mkinitfs: skipping (running in pmbootstrap)"
+	echo "mkinitfs: to force building a new initramfs, run 'mkinitfs'"
+	exit 0
+fi
+
+/usr/sbin/mkinitfs