Fix #3098

[fr-esco]

Checklist

• Issue number for this PR: #3098
• Docs included?: No
• Test units included?: No
• In a clean directory, yarn install, yarn test run successfully? Yes

Description

Running the deploy schematic on Windows:

1. Child processes that need gcloud cannot properly locate it;
2. The path to main.js is printed escaped by \\ instead of /, even though target runtime is Linux based.

Code sample

N. A.