Please remember to use WikiFormatting, to fill in the Port field, and to Cc the maintainer of that port.
In the log I see:
Undefined symbols for architecture x86_64:
"_ldif_back_initialize", referenced from:
_slap_binfo in backends.o
"_monitor_back_initialize", referenced from:
_slap_binfo in backends.o
"_hdb_back_initialize", referenced from:
_slap_binfo in backends.o
"_relay_back_initialize", referenced from:
_slap_binfo in backends.o
ld: symbol(s) not found for architecture x86_64
I also see you're building with clang, which presumably means you have a pre-release of Xcode 4.2. Try building with llvm-gcc-4.2 instead:
sudo port clean openldap
sudo port install openldap configure.compiler=llvm-gcc-4.2
If that works we can fix the port to always do that.