Ignore nested node_modules directories if parent contains no sources.
Ignore nested node_modules directories if parent contains no sources.

This in important optimization for #6037, and it also fixes #6627, since
we are now registering watchSet dependencies on the contents of
node_modules directories.

mjmasn/meteor,jdivy/meteor,4commerce-technologies-AG/meteor,lorensr/meteor,Hansoft/meteor,mjmasn/meteor,mjmasn/meteor,DAB0mB/meteor,nuvipannu/meteor,lorensr/meteor,Hansoft/meteor,nuvipannu/meteor,chasertech/meteor,jdivy/meteor,DAB0mB/meteor,4commerce-technologies-AG/meteor,lorensr/meteor,DAB0mB/meteor,lorensr/meteor,chasertech/meteor,jdivy/meteor,lorensr/meteor,nuvipannu/meteor,lorensr/meteor,DAB0mB/meteor,chasertech/meteor,mjmasn/meteor,4commerce-technologies-AG/meteor,4commerce-technologies-AG/meteor,nuvipannu/meteor,DAB0mB/meteor,chasertech/meteor,jdivy/meteor,nuvipannu/meteor,4commerce-technologies-AG/meteor,mjmasn/meteor,jdivy/meteor,chasertech/meteor,Hansoft/meteor,Hansoft/meteor,jdivy/meteor,nuvipannu/meteor,jdivy/meteor,chasertech/meteor,lorensr/meteor,chasertech/meteor,nuvipannu/meteor,4commerce-technologies-AG/meteor,Hansoft/meteor,DAB0mB/meteor,DAB0mB/meteor,mjmasn/meteor,Hansoft/meteor,Hansoft/meteor,4commerce-technologies-AG/meteor,mjmasn/meteor