This tells EShell where to look for EModules. Best practice is to
define the directory in your CPPFLAGS and then pass it to EShell at
instantiation time, like so:
Makefile.am:
evolution_CPPFLAGS = \
-DMODULEDIR=\""$(moduledir)"\"
...
main.c:
shell = g_object_new (
E_TYPE_SHELL, "module-directory", MODULEDIR, ...);