CI: Run "Test on Alpine" in Alpine v3.22 chroot

To fix this error:

    > Installing base system
    ( 1/27) Installing alpine-baselayout-data (3.7.1-r8)
    ( 2/27) Installing musl (1.2.5-r21)
    ( 3/27) Installing busybox (1.37.0-r29)
      Executing busybox-1.37.0-r29.post-install
      * unshare: Invalid argument
    ERROR: lib/apk/exec/busybox-1.37.0-r29.post-install: exited with error 127

I don't know why this is happening.
The latest Alpine comes with apk-tools 3.0.1. However, I tried to update
apk-tools in alpine-make-vm-image to 3.0.1 and it worked fine on Ubuntu,
including package scripts executed inside chroot from the configure
script.

Author: jirutka

.github/workflows/ci.yml

@@ -80,8 +80,11 @@ jobs:
       # We must run this outside the chroot.
       - run: sudo modprobe nbd max_part=16
 
-      - name: Set up latest Alpine Linux
+      - name: Set up Alpine Linux v3.22
         uses: jirutka/setup-alpine@v1
+        with:
+          # XXX: v3.23 doesn't work here, running package triggers results in "unshare: Invalid argument"
+          branch: v3.22
 
       - name: Build image for x86_64 with BIOS mode and without GPT
         run: |