ci: twister: Set PIP_ROOT_USER_ACTION=ignore

The Linux test job runs inside the Zephyr CI Docker image as root.

Signed-off-by: Stephanos Ioannidis <[email protected]>

Author: stephanosio

.github/workflows/twister.yml

@@ -132,6 +132,7 @@ jobs:
       CCACHE_REMOTE_ONLY: "true"
       # `--specs` is ignored because ccache is unable to resolve the toolchain specs file path.
       CCACHE_IGNOREOPTIONS: '-specs=* --specs=*'
+      PIP_ROOT_USER_ACTION: ignore
 
     steps:
     - name: Print cloud service information