CI: Run jlumbroso/free-disk-space before building

https://github.com/jlumbroso/free-disk-space

Considering we are missing only a few MiBs to complete the build on 6.4.5+.. That will hopefully be enough.

.github/workflows/build-current-kernel-arch.yml

@@ -66,6 +66,22 @@ jobs:
       needs.check-for-newer-kernel.outputs.new_kernel == '0'
 
     steps:
+      - name: Free Disk Space (Ubuntu)
+        uses: jlumbroso/free-disk-space@main
+        with:
+          # this might remove tools that are actually needed,
+          # if set to "true" but frees about 6 GB
+          tool-cache: false
+        
+          # all of these default to true, but feel free to set to
+          # "false" if necessary for your workflow
+          android: true
+          dotnet: true
+          haskell: true
+          large-packages: true
+          docker-images: false
+          swap-storage: true
+
       # We need to install git so the checkout is done with it
       - name: Install git
         run: pacman -Syu --noconfirm git