Patch out merged-/usr warning

On distributions other than Debian, dpkg warns on installation:

dpkg: warning: This system uses merged-usr-via-aliased-dirs, going behind dpkg's
dpkg: warning: back, breaking its core assumptions. This can cause silent file
dpkg: warning: overwrites and disappearances, and its general tools misbehavior.
dpkg: warning: See <https://wiki.debian.org/Teams/Dpkg/FAQ#broken-usrmerge>.

Other derivatives like Ubuntu or Kali patch this warning out. We should too.

See: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1035904#288 and https://bugs.launchpad.net/ubuntu/+source/dpkg/+bug/1973149