GH Actions: fix Windows caching

.github/workflows/build.yml

@@ -116,35 +116,6 @@ jobs:
       artifact-windows-win64: ${{ steps.prepare_deploy.outputs.artifact-windows-win64 }}
     steps:
 
-    - name: "[Windows] Install rsync and openssh"
-      if: runner.os == 'Windows'
-      run: |
-        $Env:PATH="c:\msys64\usr\bin;$Env:PATH"
-        pacman -S --noconfirm coreutils bash rsync openssh
-        # Unfortunately, mixing executables from msys64 and mingw (i.e. Git
-        # Bash) does not work properly and leads to errors like these:
-        #
-        #     0 [main] python3 (5248) C:\msys64\usr\bin\python3.exe: *** fatal error - cygheap base mismatch detected - 0x180347408/0x180352408.
-        #
-        # Even when prepending the MSYS2 binary directory to %PATH%, GitHub
-        # Actions will still pick the Git Bash executable over the MSYS2 one
-        # when using `shell: bash`. Since it's not feasible to set `shell` to
-        # an absolute path in a cross-platform build workflow, we overwrite the
-        # git bash executable with the MSYS2 one.
-        #
-        # Also see related issue:
-        # https://github.com/actions/virtual-environments/issues/594
-        Copy-Item -Path "C:\msys64\usr\bin\bash.exe" -Destination "C:\Program Files\Git\bin\bash.exe" -Force
-        # By default, MSYS2 uses an
-        # /etc/profile file that changes
-        # the current working directory
-        # when bash is started. We don't
-        # want this behavior,so we just
-        # delete it.
-        Remove-Item -Path "C:\msys64\etc\profile"
-        # Add MSYS2's tools to %PATH%.
-        Add-Content -Path "$Env:GITHUB_ENV" -Value "PATH=$Env:PATH"
-
     # sccache's handling of the /fp:fast MSVC compiler option is broken, so use our fork with the fix.
     # https://github.com/mozilla/sccache/issues/950
     - name: "[Windows] Set up cargo cache"
@@ -384,6 +355,39 @@ jobs:
         --dest-url 'https://downloads.mixxx.org'
         ${{ matrix.artifacts_path }}
 
+    # Warning: do not move this step before restoring caches or it will break caching due to
+    # https://github.com/actions/cache/issues/531
+    - name: "[Windows] Install rsync and openssh"
+      env:
+        SSH_PRIVATE_KEY: ${{ secrets.DOWNLOADS_HOSTGATOR_DOT_MIXXX_DOT_ORG_KEY }}
+      if: runner.os == 'Windows' && github.event_name == 'push' && env.SSH_PRIVATE_KEY != null
+      run: |
+        $Env:PATH="c:\msys64\usr\bin;$Env:PATH"
+        pacman -S --noconfirm coreutils bash rsync openssh
+        # Unfortunately, mixing executables from msys64 and mingw (i.e. Git
+        # Bash) does not work properly and leads to errors like these:
+        #
+        #     0 [main] python3 (5248) C:\msys64\usr\bin\python3.exe: *** fatal error - cygheap base mismatch detected - 0x180347408/0x180352408.
+        #
+        # Even when prepending the MSYS2 binary directory to %PATH%, GitHub
+        # Actions will still pick the Git Bash executable over the MSYS2 one
+        # when using `shell: bash`. Since it's not feasible to set `shell` to
+        # an absolute path in a cross-platform build workflow, we overwrite the
+        # git bash executable with the MSYS2 one.
+        #
+        # Also see related issue:
+        # https://github.com/actions/virtual-environments/issues/594
+        Copy-Item -Path "C:\msys64\usr\bin\bash.exe" -Destination "C:\Program Files\Git\bin\bash.exe" -Force
+        # By default, MSYS2 uses an
+        # /etc/profile file that changes
+        # the current working directory
+        # when bash is started. We don't
+        # want this behavior,so we just
+        # delete it.
+        Remove-Item -Path "C:\msys64\etc\profile"
+        # Add MSYS2's tools to %PATH%.
+        Add-Content -Path "$Env:GITHUB_ENV" -Value "PATH=$Env:PATH"
+
     - name: "Set up SSH Agent"
       if: github.event_name == 'push' && env.SSH_PRIVATE_KEY != null
       shell: bash