ci: fix git ownership error in make-rpm job

Add git safe.directory configuration before building RPMs to fix:
  fatal: detected dubious ownership in repository

This occurs when running in a container where the checkout action
creates files owned by a different user than the one running git
commands in subsequent steps.

Signed-off-by: Sarita Mahajan <sarmahaj@redhat.com>

Author: sarmahaj

.github/workflows/greenboot-ci.yaml

@@ -57,6 +57,9 @@ jobs:
           ref: ${{ needs.check-pull-request.outputs.sha }}
           allow-unsafe-pr-checkout: true
 
+      - name: Fix git ownership
+        run: git config --global --add safe.directory /__w/greenboot-rs/greenboot-rs
+
       - name: Build RPMs
         run: |
           dnf install -y git make rpm-build rust-toolset