cmake: enforce explicit artifact name

It's much easier to determine this in CI and ensure our artifact names
are correct (I have made some accidents). They (and thus the updater)
can also easily be left out of local builds -- and probably should've
always been

Signed-off-by: Seth Flynn <getchoo@tuta.io>

.github/workflows/build.yml

@@ -146,6 +146,7 @@ jobs:
       - name: Run CMake workflow
         env:
           CMAKE_PRESET: ${{ steps.cmake-preset.outputs.preset }}
+          ARTIFACT_NAME: ${{ matrix.artifact-name }}-Qt6
         run: |
           cmake --workflow --preset "$CMAKE_PRESET"