[CI] fix git errors related to directory ownership (#8628)

.github/workflows/r_tests.yml

@@ -104,6 +104,10 @@ jobs:
         # No need to add pandoc, the container has it figured out.
         apt update && apt install libcurl4-openssl-dev libssl-dev libssh2-1-dev libgit2-dev libglpk-dev libxml2-dev libharfbuzz-dev libfribidi-dev git -y
 
+    - name: Trust git cloning project sources
+      run: |
+        git config --global --add safe.directory "${GITHUB_WORKSPACE}"
+
     - uses: actions/checkout@e2f20e631ae6d7dd3b768f56a5d2af784dd54791 # v2.5.0
       with:
         submodules: 'true'