readme: add example of skipping OS dependencies

Add example of how to configure action to skip installing OS level
dependencies and Zephyr SDK

Signed-off-by: Daniel DeGrasse <ddegrasse@tenstorrent.com>

Author: danieldegrasse

README.md

@@ -73,4 +73,15 @@ the necessary modules for a West based [Zephyr workspace application][1].
     manifest-file-name: custom_west.yml
 ```
 
+## Skip installing OS level dependencies and Zephyr SDK
+
+```yaml
+- name: Setup Zephyr project
+  uses: zephyrproject-rtos/action-zephyr-setup@v1
+  with:
+    app-path: example-application
+    toolchains: arm-zephyr-eabi
+    skip-dependencies: true
+```
+
 [1]: https://docs.zephyrproject.org/latest/develop/application/index.html#zephyr-workspace-app

action.yml

@@ -162,7 +162,7 @@ runs:
         path: ${{ inputs.base-path }}/zephyr-sdk
         key: ${{ env.SDK_FILE }}-${{ inputs.toolchains }}
 
-    - if: ${{ steps.cache-toolchain.outputs.cache-hit != 'true' }}
+    - if: ${{ steps.cache-toolchain.outputs.cache-hit != 'true' && inputs.skip-dependencies != 'true' }}
       working-directory: ${{ inputs.base-path }}
       name: Download Zephyr SDK
       shell: bash