add empty `assets.zip` for placeholder

Dockerfile

@@ -14,7 +14,7 @@ RUN yarn run build && rm -rf build/*.map
 
 # build backend
 WORKDIR /cloudreve_builder/Cloudreve
-RUN zip -r assets.zip assets
+RUN zip -r - assets >assets.zip
 RUN tag_name=$(git describe --tags) \
     && export COMMIT_SHA=$(git rev-parse --short HEAD) \
     && go build -a -o cloudreve -ldflags " -X 'github.com/HFO4/cloudreve/pkg/conf.BackendVersion=$tag_name' -X 'github.com/HFO4/cloudreve/pkg/conf.LastCommit=$COMMIT_SHA'"

build.sh

@@ -32,7 +32,7 @@ buildAssets() {
   cd build
   rm -rf *.map
   cd $REPO
-  zip -r assets.zip assets
+  zip -r - assets >assets.zip
 }
 
 buildBinary() {