sdk: add vendor-qem.img into the deps list

if it exists. Fix master-without-vendor sdk_x86-sdk build

Change-Id: I5656e7124d30e71120044cce668c54793f77208a
Merged-In: I5656e7124d30e71120044cce668c54793f77208a
(cherry picked from commit a5085788115663fea0cda588b3b8dba8a9513c95)
diff --git a/core/Makefile b/core/Makefile
index 305cf4e..4fb592b 100644
--- a/core/Makefile
+++ b/core/Makefile
@@ -2856,6 +2856,7 @@
 	$(COVERAGE_ZIP) \
 	$(INSTALLED_SYSTEMIMAGE) \
 	$(INSTALLED_QEMU_SYSTEMIMAGE) \
+	$(INSTALLED_QEMU_VENDORIMAGE) \
 	$(INSTALLED_USERDATAIMAGE_TARGET) \
 	$(INSTALLED_RAMDISK_TARGET) \
 	$(INSTALLED_SDK_BUILD_PROP_TARGET) \