Gate atomics behind Rust 1.60

Signed-off-by: Joe Richey <[email protected]>

Author: josephlr

Cargo.toml

@@ -35,6 +35,10 @@ exclude = [".*"]
 # From 1.61.0, Rust supports generic types with trait bounds in `const fn`.
 zerocopy-generic-bounds-in-const-fn = "1.61.0"
 
+# From 1.60.0, Rust supports detecting if a target supports atomics, so we can
+# reliably implement traits on the Atomic* types.
+zerocopy-atomics = "1.60.0"
+
 # When the "simd" feature is enabled, include SIMD types from the
 # `core::arch::aarch64` module, which was stabilized in 1.59.0. On earlier Rust
 # versions, these types require the "simd-nightly" feature.

src/lib.rs

@@ -278,6 +278,7 @@ extern crate self as zerocopy;
 #[macro_use]
 mod macros;
 
+#[cfg(zerocopy_atomics)]
 mod atomics;
 pub mod byteorder;
 mod deprecated;