CI: Use upstream action to build snap & drop arm64 snap (#1232)

Snapd stopped working in Docker containers in commit
c6011693a8

Therefore, we cannot use the current build action,
which relies on Docker to implement cross-compilation.
Switching to the upstream build action avoids the problem at the cost
of losing the arm64 builds on amd64 hardware.
Those need to be reintroduced by some other mechanism,
e.g. via Launchpad, in the future.

Fixes #1229

.github/workflows/cd.yml

@@ -123,8 +123,8 @@ jobs:
     - name: Set Up Source
       run: rsync --filter=":- .gitignore" -r ./ pkg/snap/solvespace-snap-src
     - name: Build Snap
+      uses: snapcore/action-build@v1
       id: build
-      uses: diddlesnaps/snapcraft-multiarch-action@v1
       with:
         path: pkg/snap
     - name: Upload & Release to Edge
@@ -142,40 +142,6 @@ jobs:
         snap: ${{ steps.build.outputs.snap }}
         release: edge,beta
 
-  deploy_snap_arm64:
-    needs: [test_ubuntu, test_windows, test_macos]
-    name: Deploy ARM64 Snap
-    runs-on: ubuntu-latest
-    steps:
-    - uses: docker/setup-qemu-action@v1
-      with:
-        image: tonistiigi/binfmt@sha256:df15403e06a03c2f461c1f7938b171fda34a5849eb63a70e2a2109ed5a778bde
-    - uses: actions/checkout@v2
-    - name: Fetch Tags
-      run: git fetch --force --tags
-    - name: Set Up Source
-      run: rsync --filter=":- .gitignore" -r ./ pkg/snap/solvespace-snap-src
-    - name: Build Snap
-      id: build
-      uses: diddlesnaps/snapcraft-multiarch-action@v1
-      with:
-        path: pkg/snap
-        architecture: arm64
-    - name: Upload & Release to Edge
-      if: github.event_name == 'push'
-      uses: snapcore/action-publish@v1
-      with:
-        store_login: ${{ secrets.SNAPSTORE_LOGIN }}
-        snap: ${{ steps.build.outputs.snap }}
-        release: edge
-    - name: Upload & Release to Beta + Edge
-      if: github.event_name == 'release'
-      uses: snapcore/action-publish@v1
-      with:
-        store_login: ${{ secrets.SNAPSTORE_LOGIN }}
-        snap: ${{ steps.build.outputs.snap }}
-        release: edge,beta
-
   upload_release_assets:
     name: Upload Release Assets
     needs: [build_release_windows, build_release_windows_openmp, build_release_macos]