ci/android: Fix intermittent adb root failures

The combined $ADB wait-for-device root command can be flaky with
Cuttlefish, sometimes failing with:
"adb: unable to connect for root: closed"

Signed-off-by: Valentine Burley <valentine.burley@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/41314>

.gitlab-ci/android-runner.sh

@@ -8,8 +8,18 @@ set -uex
 
 : "${ADB:=adb}"
 
-$ADB wait-for-device root
-sleep 1
+$ADB wait-for-device
+for i in $(seq 1 5); do
+    if $ADB root; then
+        break
+    fi
+    if [ "$i" -eq 5 ]; then
+        echo "Failed to get adb root after 5 attempts"
+        exit 1
+    fi
+    sleep 2
+done
+$ADB wait-for-device
 
 # overlay