Merge pull request #1 from p-mongo/make-clean

Add a make clean target

Author: kay-kim

Makefile

@@ -15,7 +15,7 @@ TARGET_DIR=source-${GIT_BRANCH}
 # the current "stable" branch. This is weird and dumb, yes.
 STABLE_BRANCH=`grep 'manual' build/docs-tools/data/${PROJECT}-published-branches.yaml | cut -d ':' -f 2 | grep -Eo '[0-9a-z.]+'`
 
-.PHONY: help stage fake-deploy deploy deploy-search-index check-redirects publish-build-only publish migrate
+.PHONY: help stage fake-deploy deploy deploy-search-index check-redirects publish-build-only publish migrate clean
 
 help: ## Show this help message
 	@grep -E '^[a-zA-Z_-]+:.*?## .*$$' $(MAKEFILE_LIST) | sort | awk 'BEGIN {FS = ":.*?## "}; {printf "\033[36m%-20s\033[0m %s\n", $$1, $$2}'
@@ -70,3 +70,6 @@ migrate: get-assets
 
 get-assets:
 	giza generate assets
+
+clean:
+	rm -rf build