Don't build the Qt5 Mandelbrot demos unless we have Qt5

Change-Id: I968f9d9a94e3db219c7dd900db1b0261cd8f09cb
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/143397
Tested-by: Jenkins
Reviewed-by: Thorsten Behrens <thorsten.behrens@allotropia.de>
diff --git a/static/Module_static.mk b/static/Module_static.mk
index a21b235..cd37748 100644
--- a/static/Module_static.mk
+++ b/static/Module_static.mk
@@ -18,8 +18,10 @@ $(eval $(call gb_Module_add_targets,static,\
ifeq (EMSCRIPTEN,$(OS))
$(eval $(call gb_Module_add_targets,static,\
    CustomTarget_emscripten_fs_image \
    CustomTarget_wasm-qt5-mandelbrot_moc \
    Executable_wasm-qt5-mandelbrot \
    $(if $(ENABLE_QT5), \
        CustomTarget_wasm-qt5-mandelbrot_moc \
        Executable_wasm-qt5-mandelbrot \
    ) \
))
endif