Install locales used by our tests in before_install.sh

Previously this was done in the GitHub CI script, but this isn't
specific to GitHub, so do it in the common script to make these locales
also available under Cirrus CI.

Also switch to just installing locales-all instead of installing locales
and then running locale-gen because this is simpler and actually works
(locale-gen would have only worked if we modified /etc/locale.gen before
running it, but we didn't).

build/tools/before_install.sh

@@ -98,7 +98,9 @@ case $(uname -s) in
                             libglu1-mesa-dev"
             esac
 
-            pkg_install="$pkg_install $libtoolkit_dev gdb ${WX_EXTRA_PACKAGES}"
+            # Install locales used by our tests to run all the tests instead of
+            # skipping them.
+            pkg_install="$pkg_install $libtoolkit_dev gdb locales-all ${WX_EXTRA_PACKAGES}"
 
             extra_deps="$extra_deps libcurl4-openssl-dev libsecret-1-dev libnotify-dev"
             for pkg in $extra_deps; do