Flatpack example for shipping a binary package

Signed-off-by: Mitja Horvat <pinkfluid@gmail.com>

README.md

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+# Binary-Only Flatpak Package Example
+
+This demonstrates how to create a Flatpak package that distributes only a compiled binary without source code.
+
+## Project Structure
+
+- **hello.c** - Source code (kept only for development, not distributed)
+- **hello** - Compiled binary (this is what gets distributed)
+- **com.example.HelloWorld.yml** - Flatpak manifest
+
+## Key Points
+
+The Flatpak manifest uses a pre-compiled binary instead of building from source:
+
+```yaml
+modules:
+  - name: hello
+    buildsystem: simple
+    build-commands:
+      - install -D hello /app/bin/hello
+    sources:
+      - type: file
+        path: hello  # Pre-compiled binary
+```
+
+This approach:
+- Distributes only the compiled binary
+- Does not include source code in the package
+- Source file (hello.c) is excluded from distribution
+
+## Build Instructions
+
+### Option 1: Pre-compiled Binary (com.example.HelloWorld.yml)
+
+1. Compile the binary locally:
+   ```bash
+   gcc -o hello hello.c
+   ```
+
+2. Build and install the Flatpak:
+   ```bash
+   flatpak-builder --user --install --force-clean build-dir com.example.HelloWorld.yml
+   ```
+
+### Option 2: Build Inside Flatpak (com.example.HelloWorld-build-inside.yml)
+
+Build the binary inside the Flatpak sandbox using the SDK:
+
+```bash
+flatpak-builder --user --install --force-clean build-dir com.example.HelloWorld-build-inside.yml
+```
+
+This compiles `hello.c` using gcc inside the Flatpak environment, then installs only the resulting binary.
+
+### Run the Application
+
+```bash
+flatpak run com.example.HelloWorld
+```
+
+## Package for Distribution
+
+After building, create a single-file bundle for distribution:
+
+```bash
+# Create bundle from user installation
+flatpak build-bundle ~/.local/share/flatpak/repo com.example.HelloWorld.flatpak com.example.HelloWorld
+
+# Or create a custom repo and bundle
+flatpak-builder --repo=repo build-dir com.example.HelloWorld.yml
+flatpak build-bundle repo com.example.HelloWorld.flatpak com.example.HelloWorld
+```
+
+The resulting `.flatpak` file contains only the compiled binary and can be distributed to users.
+
+### Install from Bundle
+
+Users can install your package:
+```bash
+flatpak install com.example.HelloWorld.flatpak
+```
+
+## Notes
+
+- The source file (hello.c) is never included in the Flatpak package
+- Only the compiled binary is distributed
+- You can delete hello.c after building if desired

com.example.HelloWorld.yml

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+app-id: com.example.HelloWorld
+runtime: org.freedesktop.Platform
+runtime-version: '23.08'
+sdk: org.freedesktop.Sdk
+command: hello
+finish-args:
+  - --share=ipc
+  - --socket=fallback-x11
+  - --socket=wayland
+modules:
+  - name: hello
+    buildsystem: simple
+    build-commands:
+      - gcc -o hello hello.c
+      - install -D hello /app/bin/hello
+    sources:
+      - type: file
+        path: hello.c

hello.c

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+#include <stdio.h>
+
+int main() {
+    printf("Hello from Flatpak binary package!\n");
+    return 0;
+}