Based on Ubuntu 16.04 instructions here
First, install Docker, then run the following:
sudo docker run --rm -ti -v /tmp/.X11-unix:/tmp/.X11-unix -v $HOME:/root -e DISPLAY=unix$DISPLAY transistor1/remmina_devel bash
Note: change transistor1/remmina_devel to transistor1/remmina_devel:jessie if you're building for Debian Jessie.
You'll be dropped into a bash shell within the Docker container. Then, run:
/build.sh
All of the source should be downloaded automatically, and as long as both the freerdp and the remmina master branches are not broken, it should automatically compile the next branch of both.
When you're asked any questions, simply press Enter to select the defaults. This is just checkinstall building some simple .deb packages for you.
You may get error messages like these; there is no need to worry about them:
** (remmina:24462): WARNING **: Could not open X display
No protocol specified
Unable to init server: Could not connect: Connection refused
(remmina:24462): Gtk-WARNING **: cannot open display: unix:0.0
After building, when you exit the Docker container, you should see a new folder, remmina_devel, in your user's $HOME directory, with subfolders FreeRDP and Remmina. In them, there will be a freerdp_YYYYMMDD-1_amd64.deb, and a remmina_YYYYMMDD-1_amd64.deb, respectively.
You can then install these .debs on your host system. Just be aware that they don't have any dependency information baked in, so you will probably have to install other packages in order to get them to work. To get an idea of some of the libraries you may need, see my Dockerfile source for Debian, or for Ubuntu 16.04.
If the source doesn't build, you can try checking out a different branch in the FreeRDP and Remmina sources, and the run /build again.
transistor1/remmina_devel:latest - Ubuntu latest
transistor1/remmina_devel:jessie - Debian jessie