Rewrite ForceVariableDialog. It's not based on wx.TextEntryDialog

Don't customize standard wx.TextEntryDialog on the fly, implement your
own dialog for that with expected behavior and without any hacks.

     1

     2

                  <xsd:element name="Linux">

     3

                    <xsd:complexType>

     4

                      %(toolchain_gcc)s

     5

                    </xsd:complexType>

     6

                  </xsd:element>