[REG 5.9 -> 5.12] UIC --dependencies reports global headers

When asking UIC to generate a list of dependencies with uic --dependencies on a file that specifies <includes><include location="global">... or <customwidgets><customwidget><header location="global">..., these global includes are output. This is problematic because they end up in the Makefile as dependencies and are not found by make.

Example foo.ui:

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
  <class>Foo</class>
  <widget class="QWidget" name="Foo">
    <layout class="QVBoxLayout" name="verticalLayout">
      <item>
        <widget class="QwtPlot" name="plot"/>
      </item>
    </layout>
  </widget>
  <customwidgets>
    <customwidget>
      <class>QwtPlot</class>
      <extends>QFrame</extends>
      }}{{<header location="global">qwt/qwt_plot.h</header>
      }}{{ <container>1</container>
    </customwidget>
  </customwidgets>
</ui>

Expect empty output of uic -d foo.ui, but get qwt/qwt_plot.h.

Note: This should affect more versions than I marked (seems all 5.x are affected if I interpret git annotate correctly), but only tested on 5.12.4.