fix(xtask): build docs for each arch separately

Signed-off-by: Martin Kröning <[email protected]>

xtask/src/doc.rs

@@ -12,19 +12,13 @@ impl Doc {
 	pub fn run(self) -> Result<()> {
 		let sh = crate::sh()?;
 
-		let mut doc = cmd!(
-			sh,
-			"cargo doc --package hermit-kernel --no-deps --document-private-items"
-		);
-
 		for arch in Arch::all() {
 			arch.install()?;
 			let triple = arch.triple();
-			doc = doc.arg(format!("--target={triple}"));
+			cmd!(sh, "cargo doc --package hermit-kernel --no-deps --document-private-items --target={triple}")
+				.run()?;
 		}
 
-		doc.run()?;
-
 		Ok(())
 	}
 }