* Rely on libSystem when targeting macOS.
 * Make tools/gen_outline_atomics.zig more idiomatic.
 * Remove the CPU detection / auxval checking from compiler_rt. This
   functionality belongs in a different component. Zig's compiler_rt
   must not rely on constructors. Instead it will export a symbol for
   setting the value, and start code can detect and activate it.
 * Remove the separate logic for inline assembly when the target does or
   does not have lse support. `.inst` works in both cases.