Note that you can also have the nspostgres makefile use the pg_config binary which supplies info about where everything is in your postgres install.
make install POSTGRES=PG_CONFIG PG_CONFIG=/path/to/pg_config ACS=1 INST=/usr/local/aolserver AOLSERVER=/usr/local/aolserver40r10
and btw INST and AOLSERVER should probably point to the same thing, the prefix where aolserver is installed.
-Jim