Recent versions of bindgen use `std::os::raw` over `libc`, but currently
`libsqlite3-sys` is overriding that. `std::os::raw` is a subset of
`libc` that exports only the relevant type definitions, but not any
functions which require additional linking. This enables
`libsqlite3-sys` to be more easily used on targets that may not have a
libc available (presumably sqlite itself would have been compiled with
musl in that case)
See comment in libsqlite3-sys/build.rs for details - adding this flag is
harmless if it's not present in the header, and not having it can break
builds against older SQLite versions.
* If SQLITE3_LIB_DIR is present in the environment, we use that.
* If SQLITE3_LIB_DIR is not present, we try to use pkg-config.
* If SQLITE3_LIB_DIR is not present and pkg-config fails, we fall back
to /usr/lib (if it exists).
