Workaround appstream-compose bug

Apparently, appstream-compose does not recognize .svgz icons. Given KDE's
propensity to .svgz, I'm actually surprised this didn't occur earlier, but
this must be the first time such an icon didn't also have various sized
.png as a backup.

https://pagure.io/fedora-kde/SIG/issue/600

container.yaml

@@ -7,6 +7,8 @@ flatpak:
     - kwave
     - lame
     - twolame
+    # cleanup-commands (already in runtime)
+    - gzip
     command: kwave
     rename-icon: kwave
     finish-args: |-
@@ -20,3 +22,5 @@ flatpak:
         --system-talk-name=org.freedesktop.UDisks2
         --talk-name=org.kde.kconfig.notify
         --talk-name=org.kde.KGlobalSettings
+    cleanup-commands: |
+        gunzip -c /app/share/icons/hicolor/scalable/apps/kwave.svgz > /app/share/icons/hicolor/scalable/apps/kwave.svg