Tested with r5072. Here's the error message:
fmfconv_ff.c:99:1: error: unknown type name 'ReSampleContext'
static ReSampleContext *audio_resample_ctx;
I'm not sure if Fuse is supposed to work with ffmpeg, libav, or both.
Debian only includes the latter, so worst case I'll have to build the Fuse utils without ffmpeg support.