Makefile: Add required dependencies

Some of the targets rely on others but weren't actually listed:

- init relies on containerization as it invokes cctl.
- integration relies on init as it needs the rootfs with vminitd inside.

Author: dcantah

Makefile

@@ -83,7 +83,7 @@ test:
 	@$(SWIFT) test --enable-code-coverage
 
 .PHONY: integration
-integration:
+integration: init
 ifeq (,$(wildcard bin/vmlinux))
 	@echo No bin/vmlinux kernel found. See fetch-default-kernel target.
 	@exit 1