Fix pmb zap -a permissions error

The tmp dir is owned by root, when it gets created earlier by apk running as root to store the apk progress fifo. Use another directory to work around this for now (getting close to the 3.0.0 release), we can rework the apk progress fifo later on if we want.

Fix #2491 (closed)

pmb/helpers/apk.py

@@ -238,7 +238,7 @@ def cache_clean(arch: Arch) -> None:
     # if something actually went wrong with apk...
     # So we do this dance of creating a rootfs with only the files that
     # APK needs to be happy
-    tmproot = work / "tmp" / "apk_root"
+    tmproot = work / "tmp_apk_root"  # pmb#2491: not using tmp/apk_root
     if not (tmproot / "etc/apk/repositories").exists():
         tmproot.mkdir(exist_ok=True)
         (tmproot / "var/cache").mkdir(exist_ok=True, parents=True)