Fix build error on not 64 bit arch

[ryota2357]

AtomicU64 and AtomicI64 are defined only if target_pointer_width = 64

loom/src/sync/atomic/int.rs

Lines 193 to 197 in 3ef62e2

	#[cfg(target_pointer_width = "64")]
	atomic_int!(AtomicU64, u64);
	#[cfg(target_pointer_width = "64")]
	atomic_int!(AtomicI64, i64);

But they are exported for all targets

loom/src/sync/atomic/mod.rs

Lines 10 to 12 in 3ef62e2

	mod int;
	pub use self::int::{AtomicI16, AtomicI32, AtomicI64, AtomicI8, AtomicIsize};
	pub use self::int::{AtomicU16, AtomicU32, AtomicU64, AtomicU8, AtomicUsize};

[taiki-e]

Thanks for the PR. I think we should use target_has_atomic = "64" instead of target_pointer_width = "64".

[ryota2357]

Thanks, I changed to target_has_atomic = 64. This seems to be better.