This reverts commit fa445d86a110f1171b75824fe5ec139089fa4733.

Narrator: It did, in fact, make a difference.

For whatever reason, building LLVM against spacemit_x60 or baseline makes no
noticeable difference in terms of performance, but building the Zig compiler
against spacemit_x60 does. Also, the miscompilation that was causing
riscv64-linux-debug to fail was in the LLVM libraries, not in the Zig compiler,
so we may as well take the win here.