Don't use SSE on freestanding

[pixelherodev]

A better solution might be to have an option to disable/enable SSE/SIMD within the current scope, but this at least results in functional code.

[LemonBoy]

Ideally -mllvm -mattr=-sse should work too.

[andrewrk]

I think it's time to prioritize #2883

[andrewrk]

@pixelherodev can you do the equivalent changes here?

zig/src/codegen.cpp

Lines 8766 to 8783 in 8af6c7e

	if (g->zig_target->is_native) {
	if (target_supports_clang_march_native(g->zig_target)) {
	args.append("-march=native");
	}
	} else {
	args.append("-target");
	args.append(buf_ptr(&g->llvm_triple_str));
	if (target_is_musl(g->zig_target) && target_is_riscv(g->zig_target)) {
	// Musl depends on atomic instructions, which are disabled by default in Clang/LLVM's
	// cross compilation CPU info for RISCV.
	// TODO: https://github.com/ziglang/zig/issues/2883
	args.append("-Xclang");
	args.append("-target-feature");
	args.append("-Xclang");
	args.append(riscv_default_features);
	}
	}

These are for flags passed to C.

[andrewrk]

done in f2d0d98