Fix more bustage with libxul + trace-malloc.

browser/app/Makefile.in

@@ -154,8 +154,11 @@ include $(topsrcdir)/config/config.mk
 ifndef BUILD_STATIC_LIBS
 
 ifdef NS_TRACE_MALLOC
+# when libxul is enabled, trace-malloc is part of it
+ifndef MOZ_ENABLE_LIBXUL
 EXTRA_DSO_LIBS += tracemalloc
 endif
+endif
 
 else
 include $(topsrcdir)/config/static-config.mk