building libLTO.dylib

Is there a particular method one should used to build
the libLTO.dylib from the llvm svn on darwin9? Unless I
am confused, it seems that libLTO.dylib gets built when
I do a configure and make directly in the llvm svn tree
but not when I created separate llvm_objdir directory
and execute configure and make within it. Thanks in advance
for any clarifications.