ci: retain EL10 Mock failure logs

Why:
An EL10 package failure must be diagnosable from its workflow evidence.

Impact:
Failed daily-stable Mock builds now expose their direct and result-directory
logs to the existing failure-evidence upload action.

Before/After:
The workflow reported only Mock's final failed command; detailed rpmbuild
output remained inaccessible in the runner temporary directory.

Technical Overview:
Normalize ownership of the Mock result and aggregate build-log paths before
checking the build result.
On failure, write the primary log and every Mock result log to
failed-tests.log, which is already collected by upload-flake-evidence.
Keep the successful artifact path unchanged.

With the help of AI-Agents: Codex

.github/workflows/el10_daily_stable.yml

@@ -225,10 +225,17 @@ jobs:
           set -e
           devtools/ci-flake-phase.sh end \
             el10-package-build custom "$build_status"
+          sudo chown -R "$(id -u):$(id -g)" \
+            "$RUNNER_TEMP/el10-artifacts" "$RUNNER_TEMP/el10-build.log" || true
           if [ "$build_status" -eq 0 ]; then
-            sudo chown -R "$(id -u):$(id -g)" \
-              "$RUNNER_TEMP/el10-artifacts" "$RUNNER_TEMP/el10-build.log"
             cp -a "$RUNNER_TEMP/el10-artifacts" el10-daily-stable-artifacts
+          else
+            {
+              echo 'EL10 Mock build log:'
+              cat "$RUNNER_TEMP/el10-build.log"
+              find "$RUNNER_TEMP/el10-artifacts" -type f -name '*.log' \
+                -exec sh -c 'echo; echo "Mock result log: $1"; cat "$1"' sh {} \;
+            } > failed-tests.log
           fi
           exit "$build_status"