Only run ARM collection tests in main branch (apache#45068)

The ARM collection tests are testing if all tests can be properly
collected when packages not available on ARM are removed. We currently
do not have such packages, but since this is only valid for providers
and in version branches we never touch providers, we should just
skip the test on non-main branch.

.github/workflows/ci.yml

@@ -496,6 +496,7 @@ jobs:
        needs.build-info.outputs.full-tests-needed == 'true')
     with:
       test-groups: ${{ needs.build-info.outputs.test-groups }}
+      default-branch: ${{ needs.build-info.outputs.default-branch }}
       runs-on-as-json-default: ${{ needs.build-info.outputs.runs-on-as-json-default }}
       image-tag: ${{ needs.build-info.outputs.image-tag }}
       core-test-types-list-as-string: ${{ needs.build-info.outputs.core-test-types-list-as-string }}

.github/workflows/special-tests.yml

@@ -24,6 +24,10 @@ on:  # yamllint disable-line rule:truthy
         description: "The array of labels (in json form) determining default runner used for the build."
         required: true
         type: string
+      default-branch:
+        description: "The default branch for the repository"
+        required: true
+        type: string
       test-groups:
         description: "The json representing list of test test groups to run"
         required: true
@@ -199,6 +203,7 @@ jobs:
       include-success-outputs: ${{ inputs.include-success-outputs }}
       run-coverage: ${{ inputs.run-coverage }}
       debug-resources: ${{ inputs.debug-resources }}
+    if: ${{ inputs.default-branch == 'main' }}
 
   tests-system:
     name: "System test: ${{ matrix.test-group }}"