Because lld 13.0.0 is more strict about undefined references when
linking to shared libraries, it produces the following errors for zfsd:
ld: error: /home/dim/obj/home/dim/src/llvm-13-update/amd64.amd64/tmp/usr/lib/libzfs_core.so: undefined reference to libspl_assertf [--no-allow-shlib-undefined]
ld: error: /home/dim/obj/home/dim/src/llvm-13-update/amd64.amd64/tmp/usr/lib/libnvpair.so: undefined reference to libspl_assertf [--no-allow-shlib-undefined]
ld: error: /home/dim/obj/home/dim/src/llvm-13-update/amd64.amd64/tmp/usr/lib/libavl.so: undefined reference to libspl_assertf [--no-allow-shlib-undefined]
*** [zfsd.full] Error code 1
Fix this by adding libspl (where libspl_assertf lives) to zfsd's LIBADD.
MFC after: 3 days
9fae476669