Fix error for cargo check --workspace --all-targets

This prevents rust-analyzer from showing an error for the panic-handler
crate.

Author: bjorn3

crates/panic-handler/Cargo.toml

@@ -5,4 +5,8 @@ authors = ["Alex Crichton <alex@alexcrichton.com>"]
 edition = "2021"
 publish = false
 
+[lib]
+test = false
+bench = false
+
 [dependencies]

testcrate/tests/addsub.rs

@@ -1,6 +1,7 @@
 #![allow(unused_macros)]
 #![cfg_attr(f128_enabled, feature(f128))]
 
+#[allow(unused_imports)] // Unused on some archs
 use testcrate::*;
 
 macro_rules! float_sum {