Fix wasm build.

primitives/Cargo.toml

@@ -27,7 +27,9 @@ frame-system = { git = "https://github.com/paritytech/substrate", branch = "mast
 hex-literal = "0.3.1"
 parity-util-mem = { version = "0.9.0", default-features = false, optional = true }
 thiserror = "1.0.23"
-zstd = { version = "0.5.0", optional = true }
+
+[target.'cfg(not(target_os = "unknown"))'.dependencies]
+zstd = "0.5.0"
 
 [dev-dependencies]
 sp-serializer = { git = "https://github.com/paritytech/substrate", branch = "master" }
@@ -56,5 +58,4 @@ std = [
 	"polkadot-core-primitives/std",
 	"bitvec/std",
 	"frame-system/std",
-	"zstd"
 ]

primitives/src/v1.rs

@@ -475,19 +475,19 @@ pub enum CompressedPoVError {
 #[cfg(feature = "std")]
 impl CompressedPoV {
 	/// Compress the given [`PoV`] and returns a [`CompressedPoV`].
-	#[cfg(feature = "std")]
+	#[cfg(not(target_os = "unknown"))]
 	pub fn compress(pov: &PoV) -> Result<Self, CompressedPoVError> {
 		zstd::encode_all(pov.encode().as_slice(), 3).map_err(|_| CompressedPoVError::Compress).map(Self)
 	}
 
 	/// Compress the given [`PoV`] and returns a [`CompressedPoV`].
-	#[cfg(not(feature = "std"))]
+	#[cfg(target_os = "unknown")]
 	pub fn compress(_: &PoV) -> Result<Self, CompressedPoVError> {
 		Err(CompressedPoVError::NotSupported)
 	}
 
 	/// Decompress `self` and returns the [`PoV`] on success.
-	#[cfg(feature = "std")]
+	#[cfg(not(target_os = "unknown"))]
 	pub fn decompress(&self) -> Result<PoV, CompressedPoVError> {
 		use std::io::Read;
 		const MAX_POV_BLOCK_SIZE: usize = 32 * 1024 * 1024;
@@ -511,13 +511,13 @@ impl CompressedPoV {
 	}
 
 	/// Decompress `self` and returns the [`PoV`] on success.
-	#[cfg(not(feature = "std"))]
+	#[cfg(target_os = "unknown")]
 	pub fn decompress(&self) -> Result<PoV, CompressedPoVError> {
 		Err(CompressedPoVError::NotSupported)
 	}
 }
 
-#[cfg(feature = "std")]
+#[cfg(not(target_os = "unknown"))]
 impl std::fmt::Debug for CompressedPoV {
 	fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
 		write!(f, "CompressedPoV({} bytes)", self.0.len())