BUG: Propagate BUILD_SHARED_LIBS=OFF in superbuild.

If BUILD_SHARED_LIBS was set to OFF for the superbuild, it
 was not being propagated to subprojects.

Change-Id: Ib49e6c2e0d5d2cb15e23a7bb030ff8191ce18927
Merge topic 'BuildShared'

5a68eff BUG: Propagate BUILD_SHARED_LIBS=OFF in superbuild.