It looks like it would be a trivial fix with
`-Wno-shift-negative-value`, but in the end it fails with:
```
[100%] Linking C executable aften
libaften_static.a(a52enc.o): In function `aften_encode_init':
a52enc.c:(.text+0x303c): undefined reference to `apply_simd_restrictions'
collect2: error: ld returned 1 exit status
```
So it looks like it's not simply a warning issue.
Aften is an audio encoder which generates compressed audio streams based on
ATSC A/52 specification. This type of audio is also known as AC-3 or Dolby®
Digital and is one of the audio codecs used in DVD-Video content.
Homepage: http://aften.sourceforge.net/
