onlineupdate: error: statement with no effect

Actually enable NSS on non-WNT/Mac platforms.

Change-Id: Ib465d0175878bc2846a4d779b3b34ca57e55462e

onlineupdate/Executable_mar.mk

@@ -24,7 +24,10 @@ $(eval $(call gb_Executable_add_libs,mar,\
 ))
 endif
 
+ifeq ($(filter WNT MACOSX,$(OS)),)
 $(eval $(call gb_Executable_use_externals,mar,nss3))
+$(eval $(call gb_Executable_add_defs,mar,-DMAR_NSS))
+endif
 
 $(eval $(call gb_Executable_add_cobjects,mar,\
 	onlineupdate/source/libmar/src/mar_create \