git-artifacts: fix BUILD_ONLY handling for ARM64

The workflow allows users to restrict what parts are being built. For
example, `installer-i686` will build only the 32-bit installer, not the
64-bit one nor any MinGit flavor.

However, this logic was not extended when introducing support for ARM64:
Instead, we _also_ built the ARM64 installer when the user asked for
`installer-i686`.

Let's allow restricting to `installer-i686` _without_ building the ARM64
version, and allow restricting to `installer-arm64` _just_ for the ARM64
version.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Author: dscho

.github/workflows/git-artifacts.yml

@@ -338,9 +338,14 @@ jobs:
       - name: Determine whether this job should be skipped
         shell: bash
         run: |
+          suffix=${{matrix.arch.name}}
+          if test true = ${{matrix.arch.arm64}}
+          then
+            suffix=arm64
+          fi
           case " $BUILD_ONLY " in
           '  ') ;; # not set; build all
-          *" ${{matrix.artifact.name}} "*|*" ${{matrix.artifact.name}}-${{matrix.arch.name}} "*) ;; # build this artifact
+          *" ${{matrix.artifact.name}} "*|*" ${{matrix.artifact.name}}-$suffix "*) ;; # build this artifact
           *) echo "SKIP=true" >>$GITHUB_ENV;;
           esac
       - name: Download pkg-${{matrix.arch.name}}