document the system dependencies

README.md

@@ -5,7 +5,12 @@
 GG is a GUI for the version control system [Jujutsu](https://github.com/martinvonz/jj). It takes advantage of Jujutsu's composable primitives to present an interactive view of your repository. Just imagine: what if you were always in the middle of an interactive rebase, but this was actually good?
 
 ## Installation
-GG is a desktop application with a keyboard & mouse interface, written in [Tauri](https://tauri.app/). Binaries are available for several platforms on the [releases page](https://github.com/gulbanana/gg/releases). Use the `.dmg` or `.app.tar.gz` on MacOS, and the `.msi` or `.exe` on Windows. To build from source, run `npm install` followed by `npm run tauri build`.
+GG is a desktop application with a keyboard & mouse interface, written in [Tauri](https://tauri.app/). Binaries are available for several platforms on the [releases page](https://github.com/gulbanana/gg/releases). Use the `.dmg` or `.app.tar.gz` on MacOS, and the `.msi` or `.exe` on Windows.
+
+To build from source:
+1. install the system dependencies (on Debian-likes, `apt install libpango1.0-dev libatk1.0-dev libgdk-pixbuf2.0-dev libgtk-3-dev libjavascriptcoregtk-4.1-dev libwebkit2gtk-4.1-dev`)
+2. install the JS dependencies `npm install`
+3. build the rust code `npm run tauri build`
 
 ### Setup 
 Put `gg` on your path and run it from a Jujutsu workspace, pass the workspace directory as an argument or launch it separately and use the Repository->Open menu item. Tips:
@@ -47,4 +52,4 @@ Some useful commands:
 * `npm run tauri build -- --target universal-apple-darwin` - create a fat binary for MacOS.
 * `npm run tauri dev -- -- -- --debug` - run locally with --debug. Yes, all three `--` are necessary.
 
-[DESIGN.md](DESIGN.md) has some basic information about how GG works.
+[DESIGN.md](DESIGN.md) has some basic information about how GG works.