[jenkins] Add support to build.sh for timing out the build. (#5952)

* [jenkins] Add support to build.sh for timing out the build.

* Test timeout support

* [jenkins] Tell the world what happened.

* [jenkins] Minor announcement fix + disable test mode.

jenkins/build.sh

@@ -1,5 +1,10 @@
 #!/bin/bash -e
 
+# Script that builds xamarin-macios for CI
+#
+#     --configure-flags=<flags>: Flags to pass to --configure. Optional
+#     --timeout=<timeout>: Time out the build after <timeout> seconds.
+
 cd "$(dirname "${BASH_SOURCE[0]}")/.."
 WORKSPACE=$(pwd)
 
@@ -9,8 +14,48 @@ report_error ()
 }
 trap report_error ERR
 
-if [[ x$1 == x--configure-flags ]]; then
-	CONFIGURE_FLAGS="$2"
+timeout ()
+{
+	# create a subprocess that kills this process after a certain number of seconds
+	SELF_PID=$$
+	(
+		sleep "$1"
+		echo "Execution timed out after $1 seconds."
+		printf "❌ [Build timed out](%s/console)\\n" "$BUILD_URL" >> "$WORKSPACE/jenkins/pr-comments.md"
+		kill -9 $SELF_PID
+	)&
+	# kill the subprocess timeout if we exit before we time out
+	TIMEOUT_PID=$!
+	trap 'kill -9 $TIMEOUT_PID' EXIT
+}
+
+while ! test -z "$1"; do
+	case "$1" in
+		--configure-flags=*)
+			CONFIGURE_FLAGS="${1#*=}"
+			shift
+			;;
+		--configure-flags)
+			CONFIGURE_FLAGS="$2"
+			shift 2
+			;;
+		--timeout=*)
+			TIMEOUT="${1#*=}"
+			shift
+			;;
+		--timeout)
+			TIMEOUT="$2"
+			shift 2
+			;;
+		*)
+			echo "Unknown argument: $1"
+			exit 1
+			;;
+    esac
+done
+
+if test -n "$TIMEOUT"; then
+	timeout "$TIMEOUT"
 fi
 
 ls -la "$WORKSPACE/jenkins"