When performing multi-threaded IRGen, all of the link libraries used
for autolinking went (only) into the first object file. If the object
files were then placed in a static archive, the autolinking would only
kick in if clients that link the static library reference something in
the first object file. This causes link failures.
Make sure that we put the autolink information into each of the object
files we create when doing multi-threaded IRGen.
Fixes the rest of rdar://162400654.
