init: Use a relative symlink for ueventd to init

make doesn't seem to handle the absolute symlink from
$OUT/root/sbin/ueventd to /init well - it follows the link during
dependency resolution, decides $OUT/root/sbin/ueventd doesn't exist
because /init doesn't exist, and relinks it every time.

Change-Id: I9ca1c14fe5fa80634f51ffc51a7c73146d29d42e

init/Android.mk

@@ -36,10 +36,10 @@ include $(BUILD_EXECUTABLE)
 SYMLINKS := $(TARGET_ROOT_OUT)/sbin/ueventd
 $(SYMLINKS): INIT_BINARY := $(LOCAL_MODULE)
 $(SYMLINKS): $(LOCAL_INSTALLED_MODULE) $(LOCAL_PATH)/Android.mk
-	@echo "Symlink: $@ -> /$(INIT_BINARY)"
+	@echo "Symlink: $@ -> ../$(INIT_BINARY)"
 	@mkdir -p $(dir $@)
 	@rm -rf $@
-	$(hide) ln -sf /$(INIT_BINARY) $@
+	$(hide) ln -sf ../$(INIT_BINARY) $@
 
 ALL_DEFAULT_INSTALLED_MODULES += $(SYMLINKS)