build: codesign tarball binary on macOS

Previously, we were signing the binary that was released in the .pkg,
but not the binary released in the tarball.

PR-URL: nodejs/node#14179
Fixes: nodejs/node#11936
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Myles Borins <myles.borins@gmail.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

Makefile

@@ -617,6 +617,9 @@ $(BINARYTAR): release-only
 	cp README.md $(BINARYNAME)
 	cp LICENSE $(BINARYNAME)
 	cp CHANGELOG.md $(BINARYNAME)
+ifeq ($(OSTYPE),darwin)
+	SIGN="$(CODESIGN_CERT)" PKGDIR="$(BINARYNAME)" bash tools/osx-codesign.sh
+endif
 	tar -cf $(BINARYNAME).tar $(BINARYNAME)
 	rm -rf $(BINARYNAME)
 	gzip -c -f -9 $(BINARYNAME).tar > $(BINARYNAME).tar.gz