remove pointless export from qtConfHandleLibrary()

that variable is not modified in this scope, so there is no point in
exporting it here. it was probably a leftover from an earlier version.

amends c0cc50520.

Change-Id: Ic6f93d8c38d547308aa88ef337fe49bda004b337
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

mkspecs/features/qt_configure.prf

@@ -569,7 +569,6 @@ defineTest(qtConfExportLibrary) {
         qtConfOutputVar(assign, $$output, QMAKE_$${NAME}_VERSION_MINOR, $$member(version, 1))
         qtConfOutputVar(assign, $$output, QMAKE_$${NAME}_VERSION_PATCH, $$member(version, 2))
     }
-    export(config.output.$${output})
 }
 
 defineTest(qtConfHandleLibrary) {