The lack of sound for A52 is tied to liba52tofloat32 not being built. After poking around, it appears that this is due to a line in the configure.ac file.
Changing the line: VLC_ADD_BUILTINS([a52tofloat32])
To be: VLC_ADD_PLUGIN([a52tofloat32])
Seems to allow it to build and work. I don't know if this breaks things for other platforms or not, and can't test if it does.