use modfile flag for go tool

Author: roothorp

Makefile

@@ -666,7 +666,7 @@ bump-version-file:
 
 .PHONY: api-docs
 api-docs:
-	cd tools/toolbox && go tool crdoc --resources ../../config/crd/bases --output ../../docs/api-docs.md
+	 go tool -modfile=tools/toolbox/go.mod crdoc --resources config/crd/bases --output docs/api-docs.md
 
 .PHONY: validate-api-docs
 validate-api-docs: api-docs