detect presence of threads support in sqlite3 port

[Alexander Zhuravlev]

	Hello,

My port depends on databases/sqlite3 one. But it does not compile if
sqlite3 port has been compiled with WITH_THREADS option (pthreads
support).
I've tried to create databases/sqlite3-nonthreaded port and add
dependancy on ths port, but as far
as I can see sqlite3 and sqlite3-nothreads ports will be installing
the same libsqlite3.so.8, so I can not use LIB_DEPENDS line like this:

LIB_DEPENDS=    sqlite3.8:${PORTSDIR}/databases/sqlite3-nothreaded

So, how can I determine the fact that the port was compiled with such 
option, so I can rise an error in my port or compile it with bundled
sqlite 3.2 library?
Any help will be much appreciated.

Thank you.
-- 
Alexander Zhuravlev