I think I found the problem installing on OS X. In the ./engines/Makefile, in the "install" target, the script makes the assumption that shared library files are named *.so, whereas they are named *.dylib on Darwin.
There is even a comment to that effect in the Makefile:
# XXXXX This currently only works on systems that use .so as suffix
# for shared libraries as well as for Cygwin which uses the
# dlfcn_name_converter and therefore stores the engines with .so suffix, too.