busybox: don't overwrite existing inittab

If a inittab file was already provided in the skeleton, don't overwrite
it with the one that comes with the busybox package.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/busybox/busybox.mk

@@ -277,7 +277,9 @@ endif
 
 ifeq ($(BR2_INIT_BUSYBOX),y)
 define BUSYBOX_INSTALL_INITTAB
-	$(INSTALL) -D -m 0644 package/busybox/inittab $(TARGET_DIR)/etc/inittab
+	if test ! -e $(TARGET_DIR)/etc/inittab; then \
+		$(INSTALL) -D -m 0644 package/busybox/inittab $(TARGET_DIR)/etc/inittab; \
+	fi
 endef
 endif