snapcraft: unminimize iso-codes package

When building the snap in a clean environment, we start with a minimised core image. This image excludes translation
files, which are needed for the "languagelists" step. The following error will show up when building:

    Building languagelists
    do not know native name for oc
    Failed to run 'override-build': Exit code was 1.

This is due to translation files being excluded by default in /etc/dpkg/dpkg.cfg.d/excludes on minimised systems:

    # Drop all translations
    path-exclude=/usr/share/locale/*/LC_MESSAGES/*.mo

We now comment this line and reinstall the "iso-codes" package.

snapcraft.yaml

@@ -131,6 +131,10 @@ parts:
     build-packages:
       - localechooser-data
     override-build: |
+      grep '^path-exclude=.*LC_MESSAGES.*' /etc/dpkg/dpkg.cfg.d/excludes && {
+        sed -i 's/^path-exclude.*LC_MESSAGES.*/#\0/g' /etc/dpkg/dpkg.cfg.d/excludes
+        apt-get -y install --reinstall iso-codes
+      } || true
       $SNAPCRAFT_PROJECT_DIR/scripts/make-language-lists $SNAPCRAFT_PROJECT_DIR/po > $SNAPCRAFT_PART_INSTALL/languagelist
     stage:
       - languagelist