librt: honour HAS_STUBS in buildsys

Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>

librt/Makefile.in

@@ -42,6 +42,8 @@ librt_filter_SRC += $(if $(UCLIBC_HAS_ADVANCED_REALTIME),, \
 	spawn_faction_addopen.c \
 	spawn_faction_init.c)
 
+librt_filter_SRC += $(if $(UCLIBC_HAS_STUBS),,rt_stubs.c)
+
 librt_SRC := $(filter-out $(librt_filter_SRC),$(librt_SRC))
 
 librt_OBJ := $(patsubst %.c,$(librt_OUT)/%.o,$(librt_SRC))