State to synchronize detachment of spawner thread to spawned thread
const Completion = std.atomic.Value(enum(if (builtin.zig_backend == .stage2_riscv64) u32 else u8)
const Completion = std.atomic.Value(enum(if (builtin.zig_backend == .stage2_riscv64) u32 else u8) {
running,
detached,
completed,
})