build: apply rpctest tag in itest

We need to distinguish an lnd build for the purpose of integration
testing from a regular dev build. This makes it possible to adapt
parameters to let integration tests run faster (for example:
sweeper batch window).

.gitignore

@@ -28,6 +28,8 @@ _testmain.go
 /lnd-debug
 /lncli
 /lncli-debug
+/lnd-itest
+/lncli-itest
 
 # Integration test log files
 output*.log