build+ci: support macOS on arm64

Refs: #5135
Change-Id: Ifac57bf18dea805dc9eab06039806858bb3b6f20
diff --git a/.jenkins b/.jenkins
index da10d69..a9abf6d 100755
--- a/.jenkins
+++ b/.jenkins
@@ -4,6 +4,8 @@
 
 if has Linux $NODE_LABELS; then
     export PATH="${HOME}/.local/bin${PATH:+:}${PATH}"
+elif [[ -x /opt/homebrew/bin/brew ]]; then
+    eval "$(/opt/homebrew/bin/brew shellenv)"
 fi
 export CACHE_DIR=${CACHE_DIR:-/tmp}
 export WAF_JOBS=${WAF_JOBS:-1}