Perform Bazel cleanup using "--batch --max_idle_secs=1" instead of a trap.

Test: Manually.
Change-Id: Id28f504fec8c6f7222646fe822264f0a4a746825
diff --git a/build_test.bash b/build_test.bash
index a53a585..accca0f 100755
--- a/build_test.bash
+++ b/build_test.bash
@@ -43,14 +43,9 @@
     ;;
 esac
 
-function bazel_cleanup {
-  "${TOP}/tools/bazel" shutdown
-}
-trap bazel_cleanup EXIT
-
 echo
 echo "Running Bazel smoke test..."
-"${TOP}/tools/bazel" info
+"${TOP}/tools/bazel" --batch --max_idle_secs=1 info
 
 echo
 echo "Running Soong test..."