build: ignore empty folders in test-addons-napi

The same as nodejs/node#16031 except
for N-API addons.

PR-URL: nodejs/node#16380
Fixes: nodejs/node#13521
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Yuta Hiroto <hello@about-hiroppy.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>

Makefile

@@ -302,7 +302,8 @@ test/addons/.buildstamp: config.gypi \
 	test/addons/.docbuildstamp
 #	Cannot use $(wildcard test/addons/*/) here, it's evaluated before
 #	embedded addons have been generated from the documentation.
-#	Ignore folders without binding.gyp (#14843)
+#	Ignore folders without binding.gyp
+#	(https://github.com/nodejs/node/issues/14843)
 	@for dirname in test/addons/*/; do \
 		if [ ! -f "$$PWD/$${dirname}binding.gyp" ]; then \
 			continue; fi ; \
@@ -340,7 +341,11 @@ test/addons-napi/.buildstamp: config.gypi \
 	src/node_api.h src/node_api_types.h
 #	Cannot use $(wildcard test/addons-napi/*/) here, it's evaluated before
 #	embedded addons have been generated from the documentation.
+#	Ignore folders without binding.gyp
+#	(https://github.com/nodejs/node/issues/14843)
 	@for dirname in test/addons-napi/*/; do \
+		if [ ! -f "$$PWD/$${dirname}binding.gyp" ]; then \
+			continue; fi ; \
 		printf "\nBuilding addon $$PWD/$$dirname\n" ; \
 		env MAKEFLAGS="-j1" $(NODE) deps/npm/node_modules/node-gyp/bin/node-gyp \
 		        --loglevel=$(LOGLEVEL) rebuild \