Bug#727497: dh-autoreconf is already used

[Logan Rosen]

Control: retitle -1 rtaudio: update config.{sub,guess} for the AArch64 port

This package already uses dh-autoreconf, but it needs autotools-dev as
well (with the patch from above) to update config.{sub,guess}. See [1]
for more information. Please disregard Matthias's automated message.

[1] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=698765