use a more accurate hash for caching submodule objects.

.github/workflows/ci.yaml

@@ -27,12 +27,16 @@ jobs:
           sudo apt update
           sudo apt install -y libwayland-dev libxkbcommon-dev xorg-dev cmake xxd
 
+      - name: get submodule hash
+        id: get-hash
+        run: echo "HASH=$(git submodule | sha1sum)" >$GITHUB_OUTPUT
+
       - uses: actions/cache@v4
         with:
           path: lib/obj/
           # I swear to god, if runner.arch displays x64 for x86_64, I will eat a potato.
           # note: it is... fucking shit.
-          key: ${{runner.os}}_${{runner.arch}}-lib/obj-${{github.sha}}
+          key: ${{runner.os}}_${{runner.arch}}-lib/obj-${{steps.get-hash.outputs.HASH}}
           restore-keys: ${{runner.os}}_${{runner.arch}}-lib/obj-
       - run: make -Bj libs
       - run: make -j all