[libclc] Restore linking against dynamic libLLVM for out-of-tree builds

This fixes a regression where building against an installation without
the static libraries would fail. This just reinstates the old behaviour
for out-of-tree builds, assuming that in-tree builds (which still aren't
officially supported) will have the static libraries available. We can
refine this as we move towards supporting in-tree builds.

GitOrigin-RevId: 8461d901a770516cf2069fe3bce979a6f8fc8d76
1 file changed