message: fix(source map): fix inline source map comment slicing
diff: @@ -114,7 +114,7 @@ impl Compiler {
  ),
  Some(v) => v,
  };
  - let encoded = &s[idx + s.len()..];
  + let encoded = &fm.src[idx + s.len()..];
  let res = base64::decode(encoded.as_bytes())
  .context("failed to decode base64-encoded source map")?;
  