memrchr() signature is not exposed by default for NetBSD. If one does
not add -D_NETBSD_SOURCE, the compiler uses its own signature for
memrchr() that returns a 32-bit integer, leading to misbehaviour in some
situations. Defining _BSD_SOURCE doesn't work, so we define
_NETBSD_SOURCE.
memrchr() signature is not exposed by default for NetBSD. If one does not add -D_NETBSD_SOURCE, the compiler uses its own signature for memrchr() that returns a 32-bit integer, leading to misbehaviour in some situations. Defining _BSD_SOURCE doesn't work, so we define _NETBSD_SOURCE.