It's pretty easy, just follow these instructions:
https://raw.github.com/coblee/litecoin/master/doc/build-unix.txt
So you edit the makefile.unix to something like below changing to proper version number for the .a file.
$(DEPSDIR)/lib/libdb_cxx-5.1.a \
I installed the db
>sudo apt-get install libdb5.1++-dev
and added the library to the build path like coblee told me and it compile !