QProcess/Windows: Include PID in pipe names

Although qt_create_pipe() tries again if the pipe name is already
in use, it doesn't handle the case when another user has created
the pipe with the name (the error is "access denied" in that case).
The chance that it happens is small, but it can be entirely
eliminated by including a unique part in the pipe name, in this
case the PID.

[ChangeLog][Windows] Named pipes internally created by QProcess now
contain the PID in their name to ensure uniqueness.

Change-Id: I079f1b68695c1ddea3eccad241061d11e08b60f4
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/io/qprocess_win.cpp

@@ -102,7 +102,7 @@ static void qt_create_pipe(Q_PIPE *pipe, bool isInputPipe)
         // ### The user must make sure to call qsrand() to make the pipe names less predictable.
         // ### Replace the call to qrand() with a secure version, once we have it in Qt.
         _snwprintf(pipeName, sizeof(pipeName) / sizeof(pipeName[0]),
-                L"\\\\.\\pipe\\qt-%X", qrand());
+                L"\\\\.\\pipe\\qt-%lX-%X", long(QCoreApplication::applicationPid()), qrand());
 
         DWORD dwOpenMode = FILE_FLAG_OVERLAPPED;
         DWORD dwOutputBufferSize = 0;