package/fltk: add optional xlib_libXrender dependency

xlib_libXrender is enabled by default and has been added since version
1.3.4-1 and
https://github.com/fltk/fltk/commit/a6c4b29a184ce7708819f4706877eedcd99a30f5

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/fltk/fltk.mk

@@ -54,4 +54,11 @@ else
 FLTK_CONF_OPTS += --disable-xinerama
 endif
 
+ifeq ($(BR2_PACKAGE_XLIB_LIBXRENDER),y)
+FLTK_DEPENDENCIES += xlib_libXrender
+FLTK_CONF_OPTS += --enable-xrender
+else
+FLTK_CONF_OPTS += --disable-xrender
+endif
+
 $(eval $(autotools-package))