Prepare qdoc bot for a build change.

The change is needed by qdoc to work after
https://codereview.qt-project.org/#change,51141



Change-Id: I4e97ef5957d2afc15aa314b73a49f4a22b01029e
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Reviewed-by: Frederik Gladhorn <frederik.gladhorn@digia.com>

git-hooks/qdoc-bot

@@ -90,6 +90,7 @@ def run_qdoc(module_name):
         environment = os.environ
         environment["CCACHE_BASEDIR"] =  os.getcwd()
         environment["QT_HASH_SEED"] = "1234"
+        environment["QMAKEFLAGS"] = "CONFIG+=force_bootstrap"
         for cmd in ["/bin/sh ./configure --opensource --confirm-license --release".split()
                    , "make sub-src-qmake_all".split()
                    , ["/bin/bash", "-c", "if [ -f src/tools/Makefile ] ; then make -Csrc/tools sub-qdoc; else make -Csrc sub-qdoc ; fi"] # build qdoc