bsd.linker.mk: Detect LLD when built with PACKAGE_VENDOR

Recent versions of homebrew's LLD are built with PACKAGE_VENDOR (since
https://github.com/Homebrew/homebrew-core/commit/e7c972b6062af753e564104e58d1fa20c0d1ad7a).
This means that the -v output is now
Homebrew LLD 12.0.1 (compatible with GNU linkers) and bsd.linker.mk no
longer detects it as LLD since it only checks whether the first word is
LLD. This change allow me to build on macOS again and should unbreak the
GitHub actions CI.

Reviewed By: imp, uqs
MFC after: 3 days
Differential Revision: https://reviews.freebsd.org/D31224