installation notes of PG_CONFIG, to B&I with multiple postgresql installations errors.

[HackettJP]

Hi
AGE is great :)

simple note enhancement in README if ERROR occurs on building scenario such as ,due to multiple builds installation, some people may walk away with frustration not everyone is verse in pgxs or makefiles search forums etc, as pg_config always goes to the highest build number on system, forums changing loads of code in pg_config script bit to much work just change PG_CONFIG makefile and hard-link to the location of the pg_config. if you have multiple versions installed, sit back , sudo make install etc..

#PG_CONFIG = pg_config

PG_CONFIG=/usr/lib/postgresql/11/bin/pg_config

I use latest Posgresql 14, Postgresql 11(AGE) with posgres_fdw extension for data ingestion works a charm.