As per #17348, `NO_SYSTEM_FROM_IMPORTED` is supposed to be set on the consuming target of a library. That means if a target A link to both imported targets B and C, setting `NO_SYSTEM_FROM_IMPORTED` on A will result in using `-I` for both B and C. My use case is that I need to use `-I` only for one target but not the other where I want to keep `-isystem` in order to work-around some issue my toolchain. That is, I'd like to keep using `-isystem` when possible and use `-I` only for targets causing issues.