package/openjpeg: fix build with threads disabled

Fixes
http://autobuild.buildroot.net/results/f16/f16a558c30199a92e93a31e0ba391b99a9bd689f/

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/openjpeg/openjpeg.mk

@@ -15,4 +15,10 @@ OPENJPEG_DEPENDENCIES += $(if $(BR2_PACKAGE_LIBPNG),libpng)
 OPENJPEG_DEPENDENCIES += $(if $(BR2_PACKAGE_TIFF),tiff)
 OPENJPEG_DEPENDENCIES += $(if $(BR2_PACKAGE_LCMS2),lcms2)
 
+ifeq ($(BR2_TOOLCHAIN_HAS_THREADS),y)
+OPENJPEG_CONF_OPTS += -DOPJ_USE_THREAD=ON
+else
+OPENJPEG_CONF_OPTS += -DOPJ_USE_THREAD=OFF
+endif
+
 $(eval $(cmake-package))