If automake is not installed, the port fails.
automake's aclocal and libtoolize are needed in the patch-libtool
target, but the USE_AUTOMAKE* macros introduce automake as a
build_dependency. build-depends target is after patch-libtool in the
dependency chain. Hence, PATCH_DEPEND on automake.
Pointed out by: Eric Hedstr=F6m <email@example.com> and Zhong Lun=20