Coreboot Is Now Able To Build With LLVM's Clang Easier

It's now easier to build Coreboot with the LLVM Clang compiler rather than GCC.

Coreboot developer Stefan Reinauer at Google has added Clang support to crossgcc for cross-compiling with this alternative open-source compiler rather than Clang. Running the build script with -C or --clang will yield a Clang-based toolchain.

This Clang Coreboot build support currently integrates Clang patches needed in order to successfully build Coreboot. There's this LLVM meta tracker bug for issues currently blocking upstream Clang from being able to compile Coreboot. Remaining issues revolve around an intrinsic issue with AGESA boards, being able to extract the path of libcompiler_rt, some arguments not being accepted by the integrated ARM assembler, and missing altmacro support within the integrated assembler.