test: use no-save and no-package-lock flags

Use these flags when running make coverage so that a package-lock.json
file is not generated and npm does not attempt to save the deps to a
non-existent package.json file.

PR-URL: #15196
Refs: https://github.com/nodejs/node/pull/15190/files#r136932786
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Timothy Gu <timothygu99@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

Makefile

@@ -139,8 +139,9 @@ coverage: coverage-test
 coverage-build: all
 	mkdir -p node_modules
 	if [ ! -d node_modules/istanbul-merge ]; then \
-		$(NODE) ./deps/npm install istanbul-merge; fi
-	if [ ! -d node_modules/nyc ]; then $(NODE) ./deps/npm install nyc; fi
+		$(NODE) ./deps/npm install istanbul-merge --no-save --no-package-lock; fi
+	if [ ! -d node_modules/nyc ]; then \
+		$(NODE) ./deps/npm install nyc --no-save --no-package-lock; fi
 	if [ ! -d gcovr ]; then git clone --depth=1 \
 		--single-branch git://github.com/gcovr/gcovr.git; fi
 	if [ ! -d testing ]; then git clone --depth=1 \