Maybe that's helpful today, but by remaining (relatively) standards compliant the kernel codebase has a more long-term resiliency. The more tightly wedded to a single compiler implementation the greater the long term risk for the project.
If some shenanigans were to happen upstream in GCC it would not be the end of Linux.
> The Linux kernel has always traditionally been compiled with GNU toolchains such as GCC and binutils. Ongoing work has allowed for Clang and LLVM utilities to be used as viable substitutes. Distributions such as Android, ChromeOS, and OpenMandriva use Clang built kernels. LLVM is a collection of toolchain components implemented in terms of C++ objects. Clang is a front-end to LLVM that supports C and the GNU C extensions required by the kernel, and is pronounced “klang,” not “see-lang.”
If some shenanigans were to happen upstream in GCC it would not be the end of Linux.