Call brew upgrade

Author: nikic

azure/macos/brew.yml

@@ -25,11 +25,12 @@ steps:
                    zlib \
                    t1lib \
                    gd \
-                   libzip \
                    gmp \
                    tidyp \
                    libxml2 \
                    libxslt \
                    postgresql
+      # Make sure we don't get broken libzip 1.7.0
+      brew update libzip
       brew link icu4c gettext --force
     displayName: 'Install Build Dependencies'