lerna 5.6.0 ignores project level targets

A repo for simulating lerna/lerna#3407

This contains 2 sub packages with:

• Package a which depends on package b and has a test script which depends in its build script which depends on the build script of its dependencies.
• Package b which has a test script which depends on its build script.

As of lerna 5.5.4, running npm run test will execute all scripts.

Upgrading to lerna 5.6.0 suddenly causes the nx configurations in the package.json's to appear to be ignored given the build scripts are not executed anymore.

Steps to Replicate The Issue

1. Run npm ci && npm run test as is and see that Running target test for 2 project(s) and 2 task(s) they depend on is printed along with the mock scripts for those tasks.
2. Run npm install -D lerna@5.6.0 && npm run test and see Running target test for 2 project(s) is printed with no build scripts executed.