Add install package dh-autoreconf to fix gifsicle error building mm-web

Error: Cannot find module 'gifsicle'
see https://stackoverflow.com/questions/65147246/cannot-find-module-gifsicle-for-loading-image-webpack
also imagemin/gifsicle-bin#113

riffmm/scripts/riffmm-buildenv.sh

@@ -4,7 +4,7 @@
 # env variable(s) NODE_VER(unused right now) and GOLANG_VER must be set (use dockerfile ARG)
 
 # packages needed to install
-INSTALL_PKGS=( curl apt-utils gcc g++ make jq wget gnupg2 ca-certificates )
+INSTALL_PKGS=( curl apt-utils gcc g++ make jq wget gnupg2 ca-certificates dh-autoreconf )
 MM_PKGS=( build-essential libjpeg-dev libpng-dev libtiff-dev libgif-dev git )
 DEV_PKGS=( vim-tiny )