ci: fix space issues in docker

github actions keep failing due to errors like these:

failed to register layer: write /opt/toolchains/zephyr-sdk-0.17.4/xtensa-nxp_rt700_hifi4_zephyr-elf/libexec/gcc/xtensa-nxp_rt700_hifi4_zephyr-elf/12.2.0/cc1: no space left on device
Error: Docker pull failed with exit code 1

Fix this by freeing up disk space on the runner before the job runs.

Signed-off-by: Dhruva Gole <d-gole@ti.com>

Author: DhruvaG2000

.github/workflows/build.yml

@@ -9,6 +9,11 @@ jobs:
     env:
       CMAKE_PREFIX_PATH: /opt/toolchains
     steps:
+      - name: Cleanup Docker images and containers
+        run: |
+          docker system prune -af
+          docker volume prune -f
+
       - name: Checkout
         uses: actions/checkout@v4
         with: