Doc: added qmake to dependencies

Change-Id: Ib38445f8bf67e3bfe81f5d2d1a30f7b429f30ac5
Task-number: QTBUG-43810
Reviewed-by: Martin Smith <martin.smith@digia.com>
Reviewed-by: Topi Reiniö <topi.reinio@digia.com>

src/websockets/doc/qtwebsockets.qdocconf

@@ -37,7 +37,7 @@ qhp.QtWebSockets.subprojects.examples.sortPages     = true
 
 tagfile                                             = ../../../doc/qtwebsockets/qtwebsockets.tags
 
-depends                                             += qtcore qtnetwork qtdoc
+depends                                             += qtcore qtnetwork qtdoc qmake
 
 headerdirs                                          += .. \
                                                        ../../imports