Remove special-case logic for running tests on host machines

I'm not sure what process sjg@ was using, but using CHECKDIR=${.OBJDIR} with
"make check" on ^/head is the correct thing to do. This unbreaks "make check"
for me (unsandboxed, not using CHECKDIR=${.OBJDIR}).

While here, fix a whitespace nit with LIBADD.

MFC after: 1 week