This seems to fix the build with Autotools that recently started to fail
with:
autom4te-2.69: need GNU m4 1.4 or later: /usr/local/bin/gm4
aclocal: error: /usr/local/bin/autom4te-2.69 failed with exit status: 1
autoreconf-2.69: aclocal failed with exit status: 1
Closesstrongswan/strongswan#197.
