Binder RPC test: check execl return status

Also, add pragma guard to Utils.h since they are sometimes included in tests

Bug: 302723053
Test: atest binderRpcTest
Change-Id: Ic2632747375fa4847e1077d41dfa3192af68441d
diff --git a/libs/binder/Utils.h b/libs/binder/Utils.h
index b8aaf67..eec09eb 100644
--- a/libs/binder/Utils.h
+++ b/libs/binder/Utils.h
@@ -14,6 +14,8 @@
  * limitations under the License.
  */
 
+#pragma once
+
 #include <stddef.h>
 #include <sys/uio.h>
 #include <cstdint>