bring bootstrapped QT magic from qt_tool to qt_module

project files of bootstrapped modules can, just like those of
bootstrapped tools, benefit from automatic adjustment of QT (and
CONFIG).

Change-Id: I83815e69a2b105caaee0c2e2602828f8eb425eef
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>

mkspecs/features/qt_module.prf

@@ -26,6 +26,17 @@ isEmpty(VERSION):VERSION = $$QT_VERSION
 # unless overridden. Host builds are always static
 host_build|staticlib: CONFIG += static
 
+host_build {
+    QT -= gui   # no host module will ever use gui
+    force_bootstrap {
+        !build_pass: CONFIG += release
+        contains(QT, core(-private)?|xml) {
+            QT -= core core-private xml
+            QT += bootstrap-private
+        }
+    }
+}
+
 ucmodule = $$upper($$MODULE)
 
 isEmpty(MODULE_INCNAME): MODULE_INCNAME = $$TARGET

src/tools/bootstrap-dbus/bootstrap-dbus.pro

@@ -2,9 +2,7 @@ option(host_build)
 
 MODULE = bootstrap_dbus
 TARGET = QtBootstrapDBus
-QT = bootstrap-private
-CONFIG += no_module_headers internal_module
-!build_pass: CONFIG += release
+CONFIG += no_module_headers internal_module force_bootstrap
 
 DEFINES += \
     QT_NO_CAST_FROM_ASCII

src/tools/bootstrap/bootstrap.pro

@@ -2,8 +2,7 @@ option(host_build)
 
 TARGET = QtBootstrap
 QT =
-CONFIG += internal_module
-!build_pass: CONFIG += release
+CONFIG += internal_module force_bootstrap
 
 # otherwise mingw headers do not declare common functions like putenv
 win32-g++*:QMAKE_CXXFLAGS_CXX11 = -std=gnu++0x