build: add libmemif as part of build-coverity target

Change-Id: I81a3b5d0845724da40b483832a8eaed081e6e4ed
Type: improvement
Signed-off-by: Andrew Yourtchenko <ayourtch@gmail.com>
diff --git a/Makefile b/Makefile
index a7cc8d3..6950040 100644
--- a/Makefile
+++ b/Makefile
@@ -535,6 +535,7 @@
 .PHONY: build-coverity
 build-coverity:
 	$(call make,$(PLATFORM)_coverity,install-packages)
+	@make -C build-root PLATFORM=vpp TAG=vpp_coverity libmemif-install
 
 .PHONY: debug-release
 debug-release: