add --bundle-compiler-rt function to link options

and use it when building libuserland.a

The self-hosted part of stage1 relies on zig's compiler-rt, and so we
include it in libuserland.a.

This should potentially be the default, but for now it's behind a linker
option.

self-hosted translate-c: small progress on translating functions.

src/codegen.cpp

@@ -9346,6 +9346,7 @@ static Error check_cache(CodeGen *g, Buf *manifest_dir, Buf *digest) {
     cache_bool(ch, g->linker_rdynamic);
     cache_bool(ch, g->each_lib_rpath);
     cache_bool(ch, g->disable_gen_h);
+    cache_bool(ch, g->bundle_compiler_rt);
     cache_bool(ch, want_valgrind_support(g));
     cache_bool(ch, g->have_pic);
     cache_bool(ch, g->have_dynamic_link);