People are usually going to go through `make`, I don't see a reason that couldn't be instrumented to (by default) acquire an upstream GCC vs whatever forked garbage ends up in $PATH
Why would it go wrong, the ABI is stable and independent of compiler? You would hit issues with C++ but not C. I have certainly built kernels using different versions of GCC than what /lib stuff is compiled with, without issue.
You'd think that, but in effect kconfig/kbuild has many cases where they say "if the compiler supports flag X, use it" where X implies an ABI break. Per task stack protectors comes to mind.
