avoid installing php-xsl, which is a virtual package provided by php-xml on github images

.github/workflows/run-tests.yml

@@ -7,15 +7,14 @@ jobs:
     env:
       PRIMARY_HOSTNAME: box1.abc.com
       FEATURE_MUNIN: false
+      # github specific: php-xsl is a virtual package provided by php-xml
+      PHP_XSL_PACKAGE: php-xml
     steps:
       - uses: actions/checkout@v2
-      # without nanasess/setup-pup setup/webmail.sh returns "Unsupported PHP version. Required PHP >= 5.4 and < 8.0", which is generated by roundcubemail/program/include/iniset.php indicating that PHP >= 8.0
-      # However, setup/zpush.sh then fails to install package "php-xsl" with "E: Package 'php-xsl' has no installation candidate"
-      # - uses: nanasess/setup-php@master
-      #   with:
-      #     php-version: '7.2'
-      - name: update-system-php
-        run: sudo update-alternatives --set php /usr/bin/php7.2
+      # the github image comes preinstalled with multiple php versions
+      # and it sets the system php to the latest version. MIAB requires
+      # php 7.2 (the default on a new ubuntu 18 install)
+      - run: sudo update-alternatives --set php /usr/bin/php7.2
       - name: setup
         run: sudo -E tests/system-setup/remote-nextcloud-docker.sh upgrade basic
       - name: test-runner

setup/zpush.sh

@@ -17,7 +17,7 @@ source /etc/mailinabox.conf # load global vars
 
 echo "Installing Z-Push (Exchange/ActiveSync server)..."
 apt_install \
-	php-soap php-imap libawl-php php-xsl
+	php-soap php-imap libawl-php ${PHP_XSL_PACKAGE:-php-xsl}
 
 phpenmod -v php imap