take 2 of ccache for emscripten build

.github/workflows/emscripten.yml

@@ -41,13 +41,63 @@ jobs:
     steps:
     - uses: actions/checkout@v4
 
-    - uses: mymindstorm/setup-emsdk@v13
+    - uses: mymindstorm/setup-emsdk@v14
 
     - name: Prepare web data
       run: ./build-scripts/prepare-web-data.sh
 
+    - name: Install ccache
+      run: |
+        emsdk install ccache-git-emscripten-64bit
+        emsdk activate ccache-git-emscripten-64bit
+
+    - name: Get ccache vars
+      id: get-vars
+      run: |
+        echo "datetime=$(/bin/date -u "+%Y%m%d%H%M")" >> $GITHUB_OUTPUT
+        echo "ccache-path=$(echo '~/.cache/ccache')" >> $GITHUB_OUTPUT
+
+    - name: ccache cache files
+      uses: actions/cache@v4
+      with:
+        path: ${{ steps.get-vars.outputs.ccache-path }}
+        # double-dash after compiler is not a typo, it is to disambiguate between g++-<date> and g++-11-<date> for restore key prefix matching
+        key: ccache-${{ github.ref_name }}-emscripten--${{ steps.get-vars.outputs.datetime }}
+        restore-keys: |
+          ccache-master-emscripten--
+
     - name: Build with emcc (emscripten)
-      run: ./build-scripts/build-emscripten.sh
+      run: |
+        emsdk activate ccache-git-emscripten-64bit
+        # This $PATH manipulation is to work around a bug in emsdk, see
+        # https://github.com/emscripten-core/emsdk/pull/1345
+        # Once that bug is fixed, we should be able to drop this weird PATH
+        # stuff.
+        export PATH="${PATH%%:*}/../../ccache/git-emscripten_64bit/bin":$PATH
+        # The forked ccache seems to crash unless EM_CONFIG is defined, I'm not
+        # sure why this isn't figured out automatically.
+        export EM_CONFIG=$EMSDK/.emscripten
+        ccache --zero-stats
+        ccache -M 5G
+        ccache --show-stats
+
+        ./build-scripts/build-emscripten.sh
+
+    - name: post-build ccache manipulation
+      run: |
+        emsdk activate ccache-git-emscripten-64bit
+        export PATH="${PATH%%:*}/../../ccache/git-emscripten_64bit/bin":$PATH
+        ccache --show-stats
+        ccache -M 5G
+        ccache -c
+        ccache --show-stats
+
+    - name: clear ccache on PRs
+      if: ${{ github.ref_name != 'master' && !failure() }}
+      run: |
+        emsdk activate ccache-git-emscripten-64bit
+        export PATH="${PATH%%:*}/../../ccache/git-emscripten_64bit/bin":$PATH
+        ccache -C
 
     - name: Assemble web bundle
       run: ./build-scripts/prepare-web.sh

Makefile

@@ -635,6 +635,10 @@ endif
 ifeq ($(NATIVE), emscripten)
   CXX=emcc
   LD=emcc
+  ifeq ($(CCACHE), 1)
+    CXX=$(CCACHEBIN) emcc
+    LD=$(CCACHEBIN) emcc
+  endif
 
   # Flags that are common across compile and link phases.
   EMCC_COMMON_FLAGS = -sUSE_SDL=2 -sUSE_SDL_IMAGE=2 -sUSE_SDL_TTF=2 -sSDL2_IMAGE_FORMATS=['png']

build-scripts/build-emscripten.sh

@@ -2,6 +2,6 @@
 set -exo pipefail
 
 emsdk install 3.1.51
-emsdk activate 3.1.51
+emsdk activate 3.1.51 ccache-git-emscripten-64bit
 
-make -j`nproc` NATIVE=emscripten BACKTRACE=0 TILES=1 TESTS=0 RUNTESTS=0 RELEASE=1 cataclysm-tiles.js
+make -j`nproc` NATIVE=emscripten BACKTRACE=0 TILES=1 TESTS=0 RUNTESTS=0 RELEASE=1 CCACHE=1 LINTJSON=0 cataclysm-tiles.js