debian-stretch-titan: use dpkg to install libfftranscode
For some magic reason, apt segfaults while installing the DEBs:
$ apt install ./libfftranscode0_0.3_${DPKG_ARCH}.deb \ ./libfftranscode-dev_0.3_${DPKG_ARCH}.deb WARNING: apt does not have a stable CLI interface. Use with caution in scripts. Reading package lists... Segmentation fault (core dumped)
so it kind of confirms the warning about its stability ;)
