build for Linux: disable JUCE web browser (no gtk.h), vst3-only, linux install

README.md

@@ -206,24 +206,40 @@ the host map onto the factory bank.
 
 ### Prerequisites
 
-- macOS on Apple Silicon (arm64), macOS 12.0 or later
+macOS on Apple Silicon (arm64), macOS 12.0 or later:
+
 - CMake ≥ 3.22
 - A C++17 compiler (Apple Clang via Xcode / Command Line Tools)
 - `git` (to fetch the JUCE framework)
 
+Linux:
+
+- CMake ≥ 3.22, a C++17 compiler (GCC or Clang), `git`, `pkg-config`
+- Development packages used by JUCE (Debian/Ubuntu):
+  `libasound2-dev libx11-dev libxext-dev libxinerama-dev libxrandr-dev`
+  `libxcursor-dev libxcomposite-dev libfreetype6-dev libfontconfig1-dev
+  libcurl4-openssl-dev libgl1-mesa-dev`
+- No GTK/WebKit packages are needed: the plug-in does not use the web browser,
+  native file-chooser dialogs, or `<gtk/gtk.h>`.
+
 The build fetches **JUCE 8.0.4** automatically into `build/JUCE` on first
 configure - no manual JUCE setup is required.
 
 ### Commands
 
 ```sh
-make            # configure + build VST3 and AU (Release, arm64)
-make install    # build, ad-hoc codesign, and install into ~/Library/Audio/Plug-Ins
+make            # configure + build VST3 (and AU on macOS)
+make install    # build + install (~/Library/Audio/Plug-Ins on macOS, ~/.vst3 on Linux)
 make uninstall  # remove installed bundles
-make clean      # delete the build tree (and the fetched JUCE)
+make clean      # delete the CMake build tree
 make info       # print build paths
 ```
 
+On Linux the AU format is skipped automatically; only the VST3 is produced, and
+`make install` copies it to `~/.vst3` (JUCE's default Linux VST3 scan path).
+A plain `cmake -S . -B build -DJUCE_ROOT=<JUCE source> && cmake --build build`
+works on Linux as well.
+
 `make` (configure) is designed to be cheap when nothing changed and refreshes
 the git branch/hash and timestamp embedded in the LCD footer on every
 configure, so the About screen always reflects the current source state.