Eclipse: Skip generator expressions in COMPILE_DEFINITIONS (#14722)

This is a hot-fix for the bug. It seems like a good idea to generally
reform the generator to care about targets instead of directories,
but this patch at least makes the reported error go away.
Merge topic 'eclipse-hotfix' into next

311c0b98 Eclipse: Skip generator expressions in COMPILE_DEFINITIONS (#14722)
Help: Don't list debuggable properties in cmake-buildsystem manual.
Merge topic 'extend-docs' into next

0b3e98d9 Help: Don't list debuggable properties in cmake-buildsystem manual.