[clang] Detection of BOM in `#embed`-ed file

I attempted to embed a binary file that coincidentally happened to begin with the bytes `00 00 FE FF`

Specifically the first few bytes were as follows:
```
00000000: 0000 feff feff 0000 0000 0700 0000 0600 ................
```

The following error was produced:
```
fatal error: UTF-32 (BE) byte order mark detected in '...',
but encoding is not supported
```

I do not expect `#embed`-ed files to be checked for a BOM.