fix: force no_std for wasm32v1-none target regardless of std feature

cargo check --target wasm32v1-none uses workspace feature unification which
may enable the std feature even for no_std targets. wasm32v1-none (bare-metal
wasm, target_os=none) has no libstd available, so we must force no_std and
the core-as-std alias for this specific target combination.

src/lib.rs

@@ -20,12 +20,19 @@
 //! This version of arrayvec requires Rust 1.51 or later.
 //!
 #![doc(html_root_url="https://docs.rs/arrayvec/0.7/")]
-#![cfg_attr(not(feature="std"), no_std)]
+// no_std when std feature is disabled, OR when compiling for wasm32v1-none
+// (a bare-metal wasm target with no libstd, regardless of feature flags set
+// by the host workspace — cargo check --target wasm32v1-none unifies features
+// from the whole workspace which may include std=true).
+#![cfg_attr(
+    any(not(feature = "std"), all(target_arch = "wasm32", target_os = "none")),
+    no_std
+)]
 
 #[cfg(feature="serde")]
 extern crate serde;
 
-#[cfg(not(feature="std"))]
+#[cfg(any(not(feature = "std"), all(target_arch = "wasm32", target_os = "none")))]
 extern crate core as std;
 
 pub(crate) type LenUint = u32;