On the 2.4.x branch: Propose the mod_brotli Makefile fixes (r1761824,

r1771789, r1771827, r1779111) for backport.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1792806 13f79535-47bb-0310-9956-ffa450edef68