Bug 1826838 - add m4 to lint docker image. r=ahochheiden,firefox-build-system-reviewers

Required by mach configure, which we need to run for android buildconfig
tasks.

Differential Revision: https://phabricator.services.mozilla.com/D201560

taskcluster/docker/lint/system-setup.sh

@@ -11,6 +11,7 @@ apt_packages=()
 apt_packages+=('curl')
 apt_packages+=('iproute2')
 apt_packages+=('locales')
+apt_packages+=('m4')
 apt_packages+=('graphviz')
 apt_packages+=('python3-pip')
 apt_packages+=('python-is-python3')