Don't create symlinks in the build tree

This requires an update to the regression tests and/or Jenkins.
Either the regression tests must be run against installed code, or they
must be modified to not depend on the symlinks.  But that would be for
the better, as the present approach (that is removed here) is a hack
that doesn't always work, and since we want to get rid of the symlinks
in the long run, it doesn't make sense to try to make the symlinking
more elaborate.

Change-Id: I90859f1a8c15d8ac3090e31f522aae2af7ba4a67