IMO the whole idea behind building Postgres with ICU was to remove the dependency provided by the OS package. Installing ICU as shared object and configuring Postgres with the libicu*.so file may have a dependency on LD_LIBRARY_PATH. In shared object situation un-setting/re-setting the LD_LIBRARY_PATH will give inconsistent behavior. If I'm able to link ICU library to Postgres statically I'll be able to remove these dependencies.
I know there are libraries which are statically linked with the Postgres code and even Postgres internally links modules statically. I'm aiming to install ICU outside the Postgres source code directory and then link it statically. -- Sent from: http://www.postgresql-archive.org/PostgreSQL-hackers-f1928748.html
