On some platforms (anything but Linux, and on obscure Linux
architectures) dolt isn't used, so $(top_builddir)/doltlibtool
won't exist. $(top_builddir)/libtool will always be generated
even if dolt is used, so just use that unconditionally. We don't
need the extra speed when linking the single program for
introspection.
http://bugzilla.openedhand.com/show_bug.cgi?id=1699
Signed-off-by: Emmanuele Bassi <ebassi@linux.intel.com>