Remove the implicit "_" in subnames.

The NDK stub libraries need to use subname, but should use "." instead
of "_".

Test: Still builds.
Change-Id: Ib4b0303531e03968c55671ea167ab987adebd783
diff --git a/android/androidmk.go b/android/androidmk.go
index 8d2951d..7d7707f 100644
--- a/android/androidmk.go
+++ b/android/androidmk.go
@@ -146,7 +146,7 @@
 	}
 
 	if data.SubName != "" {
-		name += "_" + data.SubName
+		name += data.SubName
 	}
 
 	if data.Custom != nil {