build: check for linter in bin rather than lib

Make the "can we lint?" check in Makefile and vcbuild.bat depend on
bin/eslint.js rather than lib/eslint.js. In ESLint 4.0.0, lib/eslint.js
is not present. The lint rules call bin/eslint.js so check for that
instead.

Makefile

@@ -903,7 +903,7 @@ cpplint:
 	@$(PYTHON) tools/cpplint.py $(CPPLINT_FILES)
 	@$(PYTHON) tools/check-imports.py
 
-ifneq ("","$(wildcard tools/eslint/lib/eslint.js)")
+ifneq ("","$(wildcard tools/eslint/bin/eslint.js)")
 lint:
 	@EXIT_STATUS=0 ; \
 	$(MAKE) jslint || EXIT_STATUS=$$? ; \

vcbuild.bat

@@ -472,7 +472,7 @@ goto exit
 :jslint
 if defined jslint_ci goto jslint-ci
 if not defined jslint goto exit
-if not exist tools\eslint\lib\eslint.js goto no-lint
+if not exist tools\eslint\bin\eslint.js goto no-lint
 echo running jslint
 %config%\node tools\eslint\bin\eslint.js --cache --rule "linebreak-style: 0" --rulesdir=tools\eslint-rules --ext=.js,.md benchmark doc lib test tools
 goto exit