[sorinirimies]

Summary

Two more panics in SpirvBuilder::invoke_rustc (follow-up to #689):

-let build = cargo.output().expect("failed to execute cargo build");
+let build = cargo.output().map_err(SpirvBuilderError::CargoSpawnFailed)?;
 ...
-let stdout = String::from_utf8(build.stdout).unwrap();
+let stdout = String::from_utf8_lossy(&build.stdout).into_owned();

New variant SpirvBuilderError::CargoSpawnFailed(io::Error) — "failed to run cargo: {0}". Lossy decoding is fine: cargo's JSON messages are UTF-8, anything else on stdout is only forwarded to the user.

Evidence

multibuilder with cargo absent from PATH (only rustc present; CARGO set so cargo metadata still works):

Before (main) — panic inside spirv-builder:

thread 'main' panicked at crates/spirv-builder/src/lib.rs:1146:36:
failed to execute cargo build: Os { code: 2, kind: NotFound, message: "No such file or directory" }

After — build() returns Err; the panic is the example's own .unwrap():

thread 'main' panicked at examples/multibuilder/src/main.rs:9:34:
called `Result::unwrap()` on an `Err` value: CargoSpawnFailed(Os { code: 2, kind: NotFound, message: "No such file or directory" })

Clippy -D warnings clean.

Merge Danger

Door: two-way

Blast Radius: tiny — SpirvBuilderError is #[non_exhaustive]; only previously-panicking paths change.