Encountered this problem on Jtreg 4.2 b07

Reproduce steps:
1. Create a simple test referring jdk-repo/test/java/net/httpclient/websocket as library
http://hg.openjdk.java.net/jdk9/dev/jdk/file/b8207b069bc2/test/java/net/httpclient/websocket
Such as 9-dev/jdk/test/java/net/SampleTest.java
2. run it with jtreg
3. it will fail with following error:

#section:script_messages
----------messages:(7/371)*----------
JDK under test: C:\\jdk-9
java version "9-ea"
Java(TM) SE Runtime Environment (build 9-ea+165)
Java HotSpot(TM) 64-Bit Server VM (build 9-ea+165, mixed mode)
Library httpclient/websocket; kind: system module patches
   source directory: D:\\9-dev\\jdk\\test\\java\\net\\httpclient\\websocket
   class directory: D:\\JTwork\\classes\\java\\net\\httpclient\\websocket

#section:build
----------messages:(2/123)----------
command: build DummyWebSocketServer SampleTest
reason: User specified action: run build DummyWebSocketServer SampleTest
result: Not run. Test running...


test result: Error. can't find DummyWebSocketServer in test directory or libraries

3. move jdk.incubator.httpclient from java/net/httpclient/websocket to other place, then it is not "system module patches" library
4. re-run the test, then it works well