Fix several compiler warnings.

Change-Id: I55caa50a5937442734f4fcbdb4edf1c70f335bf8
diff --git a/tests/stubs_test.cpp b/tests/stubs_test.cpp
index d2d0ad8..9daaa22 100644
--- a/tests/stubs_test.cpp
+++ b/tests/stubs_test.cpp
@@ -34,7 +34,7 @@
   TYPE_APP
 } uid_type_t;
 
-static void check_getpwnam(const char* username, int uid, uid_type_t uid_type) {
+static void check_getpwnam(const char* username, uid_t uid, uid_type_t uid_type) {
   errno = 0;
   passwd* pwd = getpwuid(uid);
   ASSERT_TRUE(pwd != NULL);