Cirrus CI - support existing homebrew packages

diff --git a/build/ci/cirrus_ci.sh b/build/ci/cirrus_ci.sh
index 9db762f97cca7e1aa4a20b85eba9a96c5427d062..4def08374f296f751ab00d860225d037afb25164 100755 (executable)
--- a/build/ci/cirrus_ci.sh
+++ b/build/ci/cirrus_ci.sh
@@ -17,8 +17,11 @@ then
        elif [ "${UNAME}" = "Darwin" ]
        then
                set -x -e
-               brew update
-               brew install autoconf automake libtool pkg-config cmake xz lz4 zstd
+               brew update > /dev/null
+               for pkg in autoconf automake libtool pkg-config cmake xz lz4 zstd
+               do
+                       brew list $pkg > /dev/null && brew upgrade $pkg || brew install $pkg
+               done
        elif [ "${UNAME}" = "Linux" ]
        then
                if [ -f "/etc/debian_version" ]