build(dgw): add ARM64 Docker image support

[CBenoit]

Adds native ARM64 Docker images for Devolutions Gateway, enabling deployment on ARM-based devices like Raspberry Pi and AWS Graviton instances with full native performance. Multi-arch manifests automatically select the correct image for the user's platform.

Issue: DGW-325

[CBenoit]

I got the dry run to work 🟢

[Copilot]

Pull request overview

This PR adds native ARM64 Docker image support for Devolutions Gateway, enabling deployment on ARM-based systems like Raspberry Pi and AWS Graviton with full native performance. The implementation uses Docker Buildx and QEMU to build multi-architecture images with automatic platform selection via manifest lists.

Key Changes:

• Modified Dockerfile to conditionally install PowerShell for ARM64 from GitHub releases (Microsoft's APT repository lacks ARM64 support)
• Refactored release workflow to prepare separate build contexts for AMD64 and ARM64 architectures with appropriate binaries and native libraries
• Reorganized native library structure to explicitly separate platform and architecture variants (native-libs/{platform}/{arch}/)

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 6 comments.

File	Description
package/Linux/Dockerfile	Added conditional PowerShell installation logic to support both AMD64 (via APT) and ARM64 (via GitHub releases) architectures
.github/workflows/release.yml	Refactored container build process to create separate build contexts for AMD64 and ARM64, build architecture-specific images, and create multi-arch manifests
.github/workflows/package.yml	Extended Cadeau native library downloads to include ARM64 and reorganized storage structure by platform and architecture
.github/workflows/README.md	Added documentation explaining the multi-architecture Docker image build strategy

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

Incorrect path to Dockerfile and entrypoint.ps1. The 'docker' artifact uploaded in package.yml contains files at package/Linux/Dockerfile and package/Linux/entrypoint.ps1, which when downloaded will be at docker/package/Linux/Dockerfile and docker/package/Linux/entrypoint.ps1, not docker/Linux/Dockerfile. This path should be "docker/package/Linux/Dockerfile" and "docker/package/Linux/entrypoint.ps1".

Suggested change

	Copy-Item -Path "docker/Linux/Dockerfile" -Destination $PkgDir
	Copy-Item -Path "docker/Linux/entrypoint.ps1" -Destination $PkgDir
	Copy-Item -Path "docker/package/Linux/Dockerfile" -Destination $PkgDir
	Copy-Item -Path "docker/package/Linux/entrypoint.ps1" -Destination $PkgDir

[Copilot]

The hardcoded PowerShell version 7.4.6 creates a maintenance burden and could lead to version drift between architectures. Consider using a variable or ARG at the top of the Dockerfile (e.g., ARG PWSH_VERSION=7.4.6) to make version updates easier and more consistent.

[Copilot]

The docker buildx build commands lack explicit error handling. If a build fails, the script will continue to the next steps. Consider adding error checking after each docker command (e.g., if ($LASTEXITCODE -ne 0) { throw "Build failed" }) to ensure failures are caught and the workflow stops appropriately.

[Copilot]

The docker buildx build commands lack explicit error handling. If a build fails, the script will continue to the next steps. Consider adding error checking after each docker command (e.g., if ($LASTEXITCODE -ne 0) { throw "Build failed" }) to ensure failures are caught and the workflow stops appropriately.

[Copilot]

The docker buildx imagetools create commands lack explicit error handling. If manifest creation fails, the script will continue. Consider adding error checking after each command (e.g., if ($LASTEXITCODE -ne 0) { throw "Manifest creation failed" }) to ensure failures are caught and the workflow stops appropriately.

Suggested change

	Write-Host "Creating multi-arch manifest for latest..."
	docker buildx imagetools create `
	--tag "${ImageName}:latest" `
	"${ImageName}:${Version}-amd64" `
	"${ImageName}:${Version}-arm64"
	if ($LASTEXITCODE -ne 0) { throw "Manifest creation for version ${Version} failed" }
	Write-Host "Creating multi-arch manifest for latest..."
	docker buildx imagetools create `
	--tag "${ImageName}:latest" `
	"${ImageName}:${Version}-arm64"
	if ($LASTEXITCODE -ne 0) { throw "Manifest creation for latest failed" }

[Copilot]

Incorrect path to Dockerfile and entrypoint.ps1. The 'docker' artifact uploaded in package.yml contains files at package/Linux/Dockerfile and package/Linux/entrypoint.ps1, which when downloaded will be at docker/package/Linux/Dockerfile and docker/package/Linux/entrypoint.ps1, not docker/Linux/Dockerfile. This path should be "docker/package/Linux/Dockerfile" and "docker/package/Linux/entrypoint.ps1".

Suggested change

	Copy-Item -Path "docker/Linux/Dockerfile" -Destination $PkgDir
	Copy-Item -Path "docker/Linux/entrypoint.ps1" -Destination $PkgDir
	Copy-Item -Path "docker/package/Linux/Dockerfile" -Destination $PkgDir
	Copy-Item -Path "docker/package/Linux/entrypoint.ps1" -Destination $PkgDir