[commitgraph] Include in make check target.

Author: avoidscorn

Diff for: Makefile

@@ -94,6 +94,8 @@ check: ## Build all code in suitable configurations
 			   && cargo check --features fast-sha1 \
 			   && cargo check --features interrupt-handler \
 			   && cargo check --features disable-interrupts
+	cd git-commitgraph && cargo check --all-features \
+			   && cargo check
 
 unit-tests: ## run all unit tests
 	cargo test --all --no-fail-fast