Multiple checks= flags overwrite each other

[BobIsOnFire]

Passing -plugin-arg-ica-plugin checks=redundant-noexcept -plugin-arg-ica-plugin checks=improper-move will actually only enable improper-move checks. I believe that this should be handled in the same way as -plugin-arg-ica-plugin checks=redundant-noexcept,improper-move.

From the user perspective, I am thinking about following use-case:

add_ica_checks(all)
target_ica_checks(foo PRIVATE -redundant-noexcept)

This should run foo compilation with all checks but redundant-noexcept. Right now, this does not enable any check at all for foo, since ICA sees this as checks=-redundant-noexcept.