Speed up offline ISO installs

configs/profiledef.sh

@@ -12,7 +12,16 @@ bootmodes=('bios.syslinux' 'uefi.grub')
 arch="x86_64"
 pacman_conf="pacman-offline.conf"
 airootfs_image_type="squashfs"
-airootfs_image_tool_options=('-comp' 'xz' '-Xbcj' 'x86' '-b' '1M' '-Xdict-size' '1M')
+# Package archives in the offline mirror are already zstd-compressed. Storing
+# them in an outer XZ stream saves little space but makes pacman decompress XZ
+# while hashing and extracting every package during installation.
+airootfs_image_tool_options=(
+  '-comp' 'xz'
+  '-Xbcj' 'x86'
+  '-b' '1M'
+  '-Xdict-size' '1M'
+  '-action' 'uncompressed@subpathname(var/cache/omarchy/mirror/offline)'
+)
 bootstrap_tarball_compression=('zstd' '-c' '-T0' '--auto-threads=logical' '--long' '-19')
 file_permissions=(
   ["/etc/shadow"]="0:0:400"