Port ilmbase build fixes including WITH_DEBUG=yes builds.

• under WITH_DEBUG=yes builds, avoid renaming the libraries with _d suffix. (else it breaks packaging, and we don't want separate lib names) [1]
• while here, avoid creating symlinks from cmake, this causes staging violations due to cmake bug #17340, (poudriere testport) see https://gitlab.kitware.com/cmake/cmake/issues/17340
• while here, fix "make test" target - it is a left over from 2.3's gmake build. Use ctest instead. Removes TEST_TARGET.

No PORTREVISION bump necessary because each and every fixed bug would
cause a broken build and no install.

PR: 243274 [1]
Reported by: Marcin Cieslak [1] against graphics/ilmbase