charger: add charger_test

Test: charger_test
Bug: 63702641
Change-Id: Id50d024c015916cb8007742e3c17eaf1161b909f
diff --git a/healthd/charger.cpp b/healthd/charger.cpp
index ede14f2..43e7fd5 100644
--- a/healthd/charger.cpp
+++ b/healthd/charger.cpp
@@ -79,7 +79,7 @@
     struct android::BatteryProperties* /*props*/) {
 }
 
-int main(int argc, char **argv) {
+int healthd_charger_main(int argc, char** argv) {
     int ch;
 
     healthd_mode_ops = &charger_ops;
@@ -103,3 +103,9 @@
 
     return healthd_main();
 }
+
+#ifndef CHARGER_TEST
+int main(int argc, char** argv) {
+    return healthd_charger_main(argc, argv);
+}
+#endif