Add RELEASING.md to document the hybrid release process

Author: Soddentrough

RELEASING.md

@@ -0,0 +1,63 @@
+# GPUBench Release Process
+
+This document describes how GPUBench builds and publishes releases for different targets.
+
+## Release Architecture
+
+GPUBench uses a hybrid release process:
+1. **Windows Binaries**: Built and published automatically in the cloud via GitHub Actions.
+2. **Linux Packages**: Built locally on the development machine and uploaded manually using the GitHub CLI (`gh`).
+
+---
+
+## 1. Windows Releases (Automated)
+
+Windows binaries are handled by the GitHub Actions workflow in `.github/workflows/release.yml`.
+
+- **Trigger**: Pushing a tag matching `v*` (e.g. `v1.1.0.1`).
+- **Generated Assets**:
+  - `GPUBench-*-win64.zip` (Portable ZIP)
+  - `GPUBench-*-win64.exe` (NSIS Installer)
+- **Workflow**:
+  1. Commit changes and update the `BUILD_NUMBER` in `CMakeLists.txt`.
+  2. Tag the commit (e.g., `git tag v1.1.0.1`).
+  3. Push the tag to remote (`git push origin v1.1.0.1`).
+  4. The GitHub Actions runner will automatically build, package, and publish the Windows binaries to the release page.
+
+---
+
+## 2. Linux Releases (Local Dev Machine)
+
+Linux binaries (DEB, RPM, Tarball) must be built locally on the development Linux machine (which has the Vulkan SDK, OpenCL development libraries, and `glslc` compiler installed).
+
+### Step 1: Build and Package Locally
+Run the compile and packaging steps inside the local `build/` directory.
+
+> [!IMPORTANT]
+> Fedora/RedHat systems may have exported shell function definitions (like `ml` or `module` from Lmod) in the environment that cause `rpmbuild` to fail with bad exit statuses. Always package using a clean environment wrapper (`env -i`).
+
+```bash
+# Navigate to the build directory
+cd build
+
+# Configure and compile release targets
+cmake .. -DCMAKE_BUILD_TYPE=Release
+cmake --build . --parallel $(nproc)
+
+# Generate packages using a clean environment wrapper
+env -i HOME=$HOME PATH=$PATH USER=$USER cpack -G DEB
+env -i HOME=$HOME PATH=$PATH USER=$USER cpack -G RPM
+env -i HOME=$HOME PATH=$PATH USER=$USER cpack -G TGZ
+```
+
+### Step 2: Upload to GitHub Release
+Upload the generated assets directly to the existing GitHub release page using the GitHub CLI:
+
+```bash
+# Upload assets to the corresponding tag
+gh release upload v1.1.0.1 \
+  build/GPUBench-1.1.0.1-Linux.deb \
+  build/GPUBench-1.1.0.1-Linux.rpm \
+  build/GPUBench-1.1.0.1-Linux.tar.gz \
+  --clobber
+```