change unreachable Err handling

Author: Firestar99

crates/cargo-gpu/src/install.rs

@@ -12,10 +12,7 @@ use std::path::{Path, PathBuf};
 
 /// Represents a functional backend installation, whether it was cached or just installed.
 #[derive(Clone, Debug)]
-#[expect(
-    clippy::exhaustive_structs,
-    reason = "never adding private members to this struct"
-)]
+#[non_exhaustive]
 pub struct InstalledBackend {
     /// path to the `rustc_codegen_spirv` dylib
     pub rustc_codegen_spirv_location: PathBuf,
@@ -28,9 +25,8 @@ pub struct InstalledBackend {
 impl InstalledBackend {
     /// Creates a new `SpirvBuilder` configured to use this installed backend.
     #[expect(
-        clippy::missing_panics_doc,
-        clippy::expect_used,
-        reason = "unreachable"
+        clippy::unreachable,
+        reason = "it's unreachable, no need to return a Result"
     )]
     #[expect(clippy::impl_trait_in_params, reason = "forwarding spirv-builder API")]
     #[inline]
@@ -40,8 +36,11 @@ impl InstalledBackend {
         target: impl Into<String>,
     ) -> SpirvBuilder {
         let mut builder = SpirvBuilder::new(path_to_crate, target);
-        self.configure_spirv_builder(&mut builder)
-            .expect("unreachable");
+        let result = self.configure_spirv_builder(&mut builder);
+        match result {
+            Ok(()) => (),
+            Err(_) => unreachable!("we set target before calling this function"),
+        }
         builder
     }