Hide `which` stderr output

Signed-off-by: Bartol Deak <b@bdeak.net>

Makefile

@@ -82,7 +82,7 @@ assets-tarball: assets
 .PHONY: parser
 parser:
 	@echo ">> running goyacc to generate the .go file."
-ifeq (, $(shell which goyacc))
+ifeq (, $(shell which goyacc 2>/dev/null))
 	@echo "goyacc not installed so skipping"
 	@echo "To install: go install golang.org/x/tools/cmd/goyacc@v0.6.0"
 else

Makefile.common

@@ -178,7 +178,7 @@ endif
 .PHONY: common-yamllint
 common-yamllint:
 	@echo ">> running yamllint on all YAML files in the repository"
-ifeq (, $(shell which yamllint))
+ifeq (, $(shell which yamllint 2>/dev/null))
 	@echo "yamllint not installed so skipping"
 else
 	yamllint .