Synonyms for Build in:

n.

add-on, incorporate, count in, take in, involve, embrace. put together, throw up, extend, assemble, go up, put up, erect. incorporate (noun)
include, add.

v.

include (verb)
insert, add, embrace, take in, incorporate.
install (verb)
locate, graft, insert, fix, establish, connect, implant, position, install, embed, plant, Instate, put, place, ensconce, initiate, root.

Other synonyms:

add-on, add, extend, count in, involve. include. incorporate, take in, embrace. install
ensconce.
Other relevant words:
incorporate, include.