I'm getting this error when I run "make depend":

cd slapi; make -w depend make[3]: Entering directory `/vol01/developer/openldap/openldap-2.3.35/servers/slapd/slapi' ../../../build/mkdep -l -d "." -c "cc" -m "-M" -I../../../include -I.. -I. -I../../../include -I./.. -I. plugin.c slapi_pblock.c slapi_utils.c printmsg.c slapi_ops.c slapi_dn.c slapi_ext.c slapi_overlay.c plugin.c:32:18: ltdl.h: No such file or directory make[3]: Leaving directory `/vol01/developer/openldap/openldap-2.3.35/servers/slapd/slapi'

Given the configure switches I'm using, I don't think it should even be attempting to build slapi:

./configure \ --prefix=/opt/$OPENLDAP_VERSION \ --localstatedir=/var/local/$OPENLDAP_VERSION \ --sharedstatedir=/var/local/$OPENLDAP_VERSION/com \ --enable-cleartext \ --enable-crypt \ --enable-lmpasswd \ --enable-ldbm \ --enable-syncprov \ --enable-slurpd \ --without-cyrus-sasl \ --disable-slapi

This error has also occurred with previous versions (at least 2.3.27, 2.3.31, 2.3.32) but it doesn't seem to cause any functional errors as far as I can tell. (unless it's somehow related to the syncrepl problems, but that seems unlikely)