Update documentation.

Author: davidgiven

doc/building-client.md

@@ -9,31 +9,26 @@ will work wherever ImHex does. Support platforms for the FluxEngine client inclu
 well, although on Windows it'll need MSYS2 and mingw32. You'll need to
 install some support packages. **You will need to check out git with submodules enabled.**
 
-  - For Linux with Ubuntu/Debian:
-    `libudev-dev` `libsqlite3-dev` `protobuf-compiler` `libfmt-dev`
-    `libprotobuf-dev` `libmagic-dev` `libmbedtls-dev` `libcurl4-openssl-dev`
-    `libmagic-dev` `libdbus-1-dev` `libglfw3-dev` `libfreetype-dev`
-    `libboost-regex-dev` Plus, optionally (if not present, internal versions
-    will be used): `nlohmann-json3-dev` `libcli11-dev` `libmd4c-dev`
-  - For OSX with Homebrew:
-    `sqlite` `pkg-config` `libusb` `protobuf` `fmt` `make` `coreutils`
-    `dylibbundler` `libjpeg` `libmagic`  `boost` `glfw3` `ninja` `python`
-    `freetype2` `mbedtls` Plus, optionally (if not present, internal versions
-    will be used): `nlohmann-json` `cli11` `md4c` `lunasvg`
-  - For Windows with MSYS and pacboy:
-    `python` `diffutils` `ninja` `make` `zip` `mingw-w64-cross-clang`
-    `protobuf:p` `pkgconf:p` `curl-winssl:p` `file:p` `glfw:p` `mbedtls:p`
-    `sqlite:p` `freetype:p` `boost:p` `gcc:p` `binutils:p` `nsis:p`
-    `abseil-cpp:p`
-
-There may be mistakes here --- please [get in
-touch](https://github.com/davidgiven/fluxengine/issues/new) if I've missed
-anything.
+  - For Linux, see the dockerfiles in
+    [tests/docker](https://github.com/davidgiven/fluxengine/tree/master/tests/docker).
+    These are the source of truth for the dependencies and provide a known-good
+    build script.
+  - For OSX or Homebrew, see the Github CI scripts in
+    [.github/workflows/release.yml](https://github.com/davidgiven/fluxengine/blob/master/.github/workflows/release.yml).
+    These are a little harder to read (I haven't figured out how to do Windows or
+    OSX docker yet).
 
 Windows and Linux (and other Unixes) build by just doing `make`. OSX builds by
 doing `gmake` (we're using a feature which the elderly default make in OSX
-doesn't have). Parallel builds will be detected automatically; do `-j1` if for some
-reason you don't want one.
+doesn't have). Parallel builds will be detected automatically.
+
+**Note for system packagers:** During the build, some remote dependencies will
+be pulled in automatically, so you'll need a network connection. If you don't
+want this to happen, you can vendor the appropriate dependencies by placing
+them in the `dep/r` directory. Look at the `gitrepository` lines in
+[build/dep/build.py](https://github.com/davidgiven/fluxengine/blob/ab/dep/build.py)
+to see what goes where.
+
 You should end up with some executables in the current directory. The command line version
 is called `fluxengine` or `fluxengine.exe` depending on your platform,
 and the ImHex-based GUI will be `fluxengine-gui` or `fluxengine-gui.exe`.