A question about building pg-libphonenumber

OK, this seems a stupid question, but I do not see the answer.


I downloaded pg-libphonenumber, and am going to try to build it for PG
version 11. Looks like the last build was against version 9.6. 

It builds fine, the issue comes in when I try to do a make install. It
wants to install in the appropriate directory tree for 9.6. Should be a
simple thing to change, right? But greping around, I cannot seem to find
where this is defend. it is NOT in the Makefile.

Can someone tell me where to change this to try it against the version of
the DB engine I am running?

-- 
"They that would give up essential liberty for temporary safety deserve
neither liberty nor safety."
                        -- Benjamin Franklin