Revert "#359 BASIS_EXPORT_TARGETS is now an advanced user option that defaults to OFF. This improves performance noticeably, and avoids bugs in the export targets when external/imported shared libraries from other modules or projects are used."

This reverts commit 3b3027ac1a523fe3a410b265183aec638b844ef7.
#359 BASIS_EXPORT is now an option flag, and linked libraries are added to the export list.