ci: make "test" prep better cache for compiletests and difftests

Author: Firestar99

.github/workflows/ci.yaml

@@ -78,6 +78,10 @@ jobs:
           OUT_DIR: "target/debug/ci/out"
         run: cargo run -p example-runner-wgpu-builder --no-default-features --features "use-installed-tools"
 
+      - name: prep cache for compiletest and difftest
+        run: cargo build -p compiletests -p difftests --release --no-default-features --features "use-installed-tools"
+
+
   android:
     name: Android
     strategy: