java/io/pathNames/GeneralWin32.java fails on Windows when the jtreg and source dirs are on different drives.

Easily reproducible by setting the workdir (using -w:) to a different drive.

T:\\testoutput\\jtreg\\JTwork\\scratch\\0\\tmp <== tmp\\x.2\\x.4\\x.6\\..\\\\\\..\\\\\\..
C:\\\\tmp\\foo2 <-- C:tmp\\foo2 ==> C:\\tmp\\foo2 MISMATCH
java.lang.RuntimeException: Mismatch: C:tmp\\foo2 ==> C:\\tmp\\foo2, should be C:\\\\tmp\\foo2
at General.check(General.java:285)
at General.checkSlashes(General.java:323)
at General.checkNames(General.java:360)
at GeneralWin32.checkDrive(GeneralWin32.java:136)
at GeneralWin32.checkDrivePaths(GeneralWin32.java:140)
at GeneralWin32.main(GeneralWin32.java:174)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:563)
at com.sun.javatest.regtest.agent.MainActionHelper$SameVMRunnable.run(MainActionHelper.java:230)
at java.base/java.lang.Thread.run(Thread.java:844)