Add support for building vendor_ramdisk-debug.img

Existing BoardConfig.mk variable:
BOARD_BUILD_VENDOR_RAMDISK_IMAGE := true

generates:
out/target/product/<name>/vendor_ramdisk.img

Extend the above to additionally generate:
out/target/product/<name>/vendor_ramdisk-debug.img

as the two ramdisks should be built together.

Test: make
Change-Id: Ief572e30c9225d0f5569e9ff89096c69accafc7f
diff --git a/core/main.mk b/core/main.mk
index 97ed93d..d84e43e 100644
--- a/core/main.mk
+++ b/core/main.mk
@@ -1497,6 +1497,9 @@
 .PHONY: vendorramdisk
 vendorramdisk: $(INSTALLED_VENDOR_RAMDISK_TARGET)
 
+.PHONY: vendorramdisk_debug
+vendorramdisk_debug: $(INSTALLED_VENDOR_DEBUG_RAMDISK_TARGET)
+
 .PHONY: productimage
 productimage: $(INSTALLED_PRODUCTIMAGE_TARGET)
 
@@ -1556,6 +1559,7 @@
     $(INSTALLED_VENDOR_BOOTIMAGE_TARGET) \
     $(INSTALLED_VENDOR_DEBUG_BOOTIMAGE_TARGET) \
     $(INSTALLED_VENDOR_RAMDISK_TARGET) \
+    $(INSTALLED_VENDOR_DEBUG_RAMDISK_TARGET) \
     $(INSTALLED_ODMIMAGE_TARGET) \
     $(INSTALLED_VENDOR_DLKMIMAGE_TARGET) \
     $(INSTALLED_ODM_DLKMIMAGE_TARGET) \