ci: fix rjags install on windows

Author: ahasverus

.github/workflows/R-CMD-check.yaml

@@ -40,13 +40,27 @@ jobs:
           http-user-agent: ${{ matrix.config.http-user-agent }}
           use-public-rspm: true
 
+      - name: Cache JAGS (Windows)
+        if: runner.os == 'Windows'
+        uses: actions/cache@v3
+        with:
+          path: C:\Program Files\JAGS
+          key: ${{ runner.os }}-jags-4.3.1
+          restore-keys: |
+            ${{ runner.os }}-jags-
+            
       - name: Install JAGS (Windows)
         if: runner.os == 'Windows'
-        run: |
-          curl.exe -o wjags.exe --url https://deac-fra.dl.sourceforge.net/project/mcmc-jags/JAGS/4.x/Windows/JAGS-4.2.0.exe
-          wjags.exe /S
-          del wjags.exe
         shell: cmd
+        run: |
+          if not exist "C:\Program Files\JAGS\JAGS-4.3.1\bin\jags-terminal.exe" (
+            echo "JAGS not found in cache, downloading and installing..."
+            curl -o jags-installer.exe -L https://sourceforge.net/projects/mcmc-jags/files/JAGS/4.x/Windows/JAGS-4.3.1.exe/download
+            jags-installer.exe /S
+            del jags-installer.exe
+          ) else (
+            echo "JAGS found in cache, skipping installation"
+          )
         
       - name: Install JAGS (macOS)
         if: runner.os == 'macOS'