buildroot: Add the install operation of bootloader_slot [1/1]

PD#SH-22650

Problem:
When the install operation in the buildroot environment fails to install
bootloader_slot into rootfs.

Solution:
Modify the makefile to add the install operation of bootloader_slot.

Verify:
A113L2-BA400

Change-Id: I5f0285e3685acda7196ff9d0ac704858a3875526
Signed-off-by: shu.wang <shu.wang@amlogic.com>
diff --git a/bootloader_message/Makefile b/bootloader_message/Makefile
index 6b143dc..8e2a4e4 100644
--- a/bootloader_message/Makefile
+++ b/bootloader_message/Makefile
@@ -24,3 +24,4 @@
 install:
 	install -m 755 $(OUT_DIR)/$(LIB) $(STAGING_DIR)/usr/lib
 	install -m 755 $(OUT_DIR)/urlmisc $(TARGET_DIR)/usr/bin
+	install -m 755 $(OUT_DIR)/bootloader_slot $(TARGET_DIR)/usr/bin