It really should be. I added an explicit test on the configure log to make sure faac support is in there.
Furthermore, the package (and the avidemux binary) requires libfaac.so.0 and libfaad.so.0, so faac support is definitely in.
I have installed both from packman. But if i try to save a video with Video: MPEG-4 and Audio: AAC(FAAC) he says, that he can’t initialize the encoder.