installDeps.sh's only side effect should be to actually install dependencies
according to a configuration file, and not to modify it.
Adding --no-save to the npm command line forces npm to have a read only access
to package.json.
Old npm versions seem to support --no-XXX style flags even if not documented
(see https://github.com/npm/npm/issues/14285#issuecomment-254298519)
Tested with npm 3.5.2 and 6.1.0
Fixes#3396
c4918efc1b