compile_codegen: SpirvBuilder: fix query_rustc_version() for stable rustc versions

Author: Firestar99

crates/spirv-builder/src/lib.rs

@@ -1135,13 +1135,14 @@ pub fn query_rustc_version(toolchain: Option<&str>) -> std::io::Result<Version>
         cmd.arg(format!("+{}", toolchain));
     }
     cmd.arg("--version");
+    let output = cmd.output()?;
 
-    let parse = |stdout| {
-        let output = String::from_utf8(stdout).ok()?;
+    let stdout = String::from_utf8(output.stdout).expect("stdout must be utf-8");
+    let parse = |output: &str| {
         let output = output.strip_prefix("rustc ")?;
-        let version = &output[..output.find("-")?];
-        Some(Version::parse(version).expect("invalid version"))
+        let version = &output[..output.find(|c| !"0123456789.".contains(c))?];
+        Version::parse(version).ok()
     };
-
-    Ok(parse(cmd.output()?.stdout).expect("rustc --version parsing failed"))
+    Ok(parse(&stdout)
+        .unwrap_or_else(|| panic!("failed parsing `rustc --version` output `{}`", stdout)))
 }