Don't call `getArguments` unnecessarily

Remove a second call to `getArguments` by reusing the value returned
from the first call.

That call was added in Ie6dd9b13711bae65f6fd6d1a5286307cd0cf2ad3
which neglected to perform this simplification.

Change-Id: I2186db1fa3158886dc785557e977e7a25bfe4c72
diff --git a/cc/compdb.go b/cc/compdb.go
index 4132e09..3818e9c 100644
--- a/cc/compdb.go
+++ b/cc/compdb.go
@@ -193,7 +193,7 @@
 			}
 			builds[src.String()] = compDbEntry{
 				Directory: android.AbsSrcDirForExistingUseCases(),
-				Arguments: getArguments(src, ctx, ccModule, ccPath, cxxPath),
+				Arguments: args,
 				File:      src.String(),
 			}
 		}