.github/workflows: cache "patched tools"

Installing the build dependencies and building the tools takes a long
time.

Signed-off-by: Allison Karlitskaya <[email protected]>

Author: allisonkarlitskaya

.github/workflows/examples.yml

@@ -60,7 +60,6 @@ jobs:
           python3-libvirt \
           qemu-system \
           systemd-boot-efi
-        sudo apt-get build-dep systemd e2fsprogs
 
     - name: Get a newer podman for heredoc support (from plucky)
       run: |
@@ -70,10 +69,20 @@ jobs:
 
     - uses: actions/checkout@v4
 
-    - name: Install patched tools
+    - name: Check cache for patched tools
+      uses: actions/cache@v3
+      with:
+        path: ~/bin
+        key: patched-tools-bin-${{ hashFiles('examples/common/install-patched-tools') }}
+
+    - name: Ensure patched tools are installed
       run: |
-        mkdir ~/bin
-        examples/common/install-patched-tools ~/bin
+        set -eux
+        if [ ! -x "$HOME/bin/mkfs.ext4" ]; then
+          sudo apt-get build-dep systemd e2fsprogs
+          mkdir ~/bin
+          examples/common/install-patched-tools ~/bin
+        fi
 
     - name: Run example tests
       run: |