zeroize: always enable AArch64 support (#1064)

Now that our MSRV is high enough we don't need to feature-gate `aarch64`
support anymore, and instead it can be always-on when compiling for
`aarch64` targets.

The `aarch64` feature is retained as a noop since removing it would be a
breaking change.

zeroize/Cargo.toml

@@ -23,11 +23,12 @@ zeroize_derive = { version = "1.3", path = "derive", optional = true }
 
 [features]
 default = ["alloc"]
-aarch64 = []
 alloc = []
-derive = ["zeroize_derive"]
 std = ["alloc"]
 
+aarch64 = [] # NOTE: vestigial no-op feature; AArch64 support is always enabled now
+derive = ["zeroize_derive"]
+
 [package.metadata.docs.rs]
 all-features = true
 rustdoc-args = ["--cfg", "docsrs"]

zeroize/src/lib.rs

@@ -245,7 +245,7 @@ extern crate std;
 #[cfg(feature = "zeroize_derive")]
 pub use zeroize_derive::{Zeroize, ZeroizeOnDrop};
 
-#[cfg(all(feature = "aarch64", target_arch = "aarch64"))]
+#[cfg(target_arch = "aarch64")]
 mod aarch64;
 #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
 mod x86;