qt: qt3 compatibility needs gui support

Closes #2911

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

CHANGES

@@ -9,6 +9,7 @@
 
 	Issues resolved (http://bugs.uclibc.org):
 
+	#2911: Qt: Disable qt3support-option, if gui-module isn't selected
 	#3259: Unable to build webkit (on arm)
 	#3295: slang fails to build on mipsel
 	#3325: ffmpeg fails to build

package/qt/Config.in

@@ -57,6 +57,7 @@ config BR2_PACKAGE_QT_LICENSE_APPROVED
 
 config BR2_PACKAGE_QT_QT3SUPPORT
 	bool "Compatibility with Qt3"
+	depends on BR2_PACKAGE_QT_GUI_MODULE
 	help
 	  Turns on support for older Qt3. This will create an additional
 	  library with proxy code and increase the space required on target.