Today I built a compile and build environment for Domino 9.0.1 on Linux 64Bit. I had done this for 32-Bit Linux a while ago and all the steps for 32Bit also work in a 64Bit environment.
There is only one symlink you have to add in addition to the symlinks you have to create on 32-Bit
ln -s $Notes_ExecDirectory/libgsk8iccs_64.so /usr/lib64/libgsk8iccs_64.so
where $Notes_ExecDirectory=/opt/ibm/domino64/domino/notes/latest/linux in my environment