Disable OMP

[buybackoff]

It's not needed and OB docs/comments say explicitly that it's slow.

The main use case is 1 thread, but synced, so we need USE_THREAD=1.

Also need to decide if to statically link with MSVCRT, or create a package for that and link dynamically. It's already Native, LMDB, SQLite that are linked statically. This is a general issue for all of them. Not sure if it's important at all.