Cache the downloaded pandoc binary.

.github/workflows/linux.yml

@@ -16,6 +16,7 @@ concurrency:
 
 env:
   CPM_SOURCE_CACHE: ${{ github.workspace }}/cpm-cache
+  PANDOC_CACHE_DIR: ${{ github.workspace }}/pandoc-cache
 
 jobs:
   build-linux:
@@ -33,6 +34,11 @@ jobs:
         path: ${{ env.CPM_SOURCE_CACHE }}
         key: ${{ runner.os }}-cpm-${{ hashFiles('**/vendor.cmake', '**/CMakeLists.txt') }}
         restore-keys: ${{ runner.os }}-cpm-
+    - name: Cache pandoc
+      uses: actions/cache@v4
+      with:
+        path: ${{ env.PANDOC_CACHE_DIR }}
+        key: ${{ runner.os }}-pandoc-${{ hashFiles('cmake/manual.cmake') }}
     - name: Determine build parallelism
       run: |
         if [ "${ACT:-}" != "true" ] && [ "${FORGEJO_ACTIONS:-}" != "true" ]; then