Emulation has been legal in the US since the Sony vs. Bleem! case was decided. As long as they do a clean room reconstruction of the hardware's functionalities

Emulation has been legal in the US since the Sony vs. Bleem! case was decided. As long as they do a clean room reconstruction of the hardware's functionalities it remains legal. What you are aruging is essentially that clang is guilty for not using GPL because it also compiles code written for gcc. This is not how things work in OSS.