CI: don't override ccache dir

maybe this is why it isn't working?

.github/workflows/ficus.yml

@@ -12,8 +12,6 @@ env:
 jobs:
   build-ficus-toolchain:
     runs-on: ubuntu-latest
-    env:
-      CCACHE_DIR: ~/ccache-cache
     steps:
       - name: Checkout repo
         uses: actions/checkout@v3
@@ -25,14 +23,11 @@ jobs:
       - name: Install dependencies
         run: sudo apt-get update && sudo apt-get install -y cmake build-essential pax gcc g++ nasm bison bzip2 flex mtools texinfo libgmp-dev libmpfr-dev libmpc-dev xorriso ccache
 
-      - name: Create ccache dir
-        run: mkdir ~/ccache-cache
-
       - name: CCache cache
         id: cache-ccache
         uses: actions/cache@v4
         with:
-          path: ~/ccache-cache
+          path: ~/.cache/ccache
           key: ${{ runner.os }}-ccache
 
       - name: Add ccache to path