Accept apex packages as argument.

Bug: 112669193
Test: Successfully reaches PackageManager. Doesn't break existing flows.
Change-Id: If4a173e290ebf0b70beb97111a6d75400da7ec8d
diff --git a/adb/transport.h b/adb/transport.h
index 1350e63..ea97270 100644
--- a/adb/transport.h
+++ b/adb/transport.h
@@ -59,6 +59,8 @@
 extern const char* const kFeatureLibusb;
 // The server supports `push --sync`.
 extern const char* const kFeaturePushSync;
+// The server supports installing .apex packages.
+extern const char* const kFeatureApex;
 
 TransportId NextTransportId();