Fix: include path to Qt zlib

Change-Id: I8142a77d45007c69bfccc0d6d471205153e2de03
Reviewed-by: Sergio Ahumada <sergio.ahumada@digia.com>

src/3rdparty/zlib_dependency.pri

@@ -3,5 +3,5 @@ contains(QT_CONFIG, system-zlib) {
     if(unix|win32-g++*): LIBS_PRIVATE += -lz
     else:                LIBS += zdll.lib
 } else {
-    INCLUDEPATH += $$[QT_INSTALL_HEADERS]/QtZlib
+    INCLUDEPATH += $$[QT_INSTALL_HEADERS/get]/QtZlib
 }