use LODE_HOME when present to locat ant, junit and gnumake

LODE_HOME is an environment variable that stem from
the LibreOffice Development Environment... a small
project aimed at simplying the setup of a build environement
for Libreoffice, for dev, release, tinderboxing or jenkins slave
(see git://gerrit.libreoffice.org/lode )

Among other things it defines some standard locations where where
some specific tools that usually require manual install
are to be installed (and lode's ./setup take care of doing just that)

Teaching configure.ac about these location simplyfy even more
the autogen.input setup when using a lode setup.

Change-Id: I43d5c11b59110300f69dadfb7fd1c96e94f81652