The change in commit 27252b24 (cmComputeLinkInformation: Simplify
generator object access, 2015-08-02) broke the conditional use of a
target introduced in commit 41abdc17 (cmGeneratorTarget: Move GetSOName
from cmTarget, 2015-08-04). Restore the conditional lookup. Add a test
case that hacks platform information variables to trigger this code
everywhere.
Brad King