[Process] Use new ProcessUtils::escapeArgument to escape ProcessBuilder prefix
[Process] Do not throw LogicException in ProcessBuilder::getProcess if no arguments are set but a prefix is
merged branch romainneutron/process-builder (PR #7821)

This PR was merged into the master branch.

Discussion
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[Process] Fix two process-builder minor bugs

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| License       | MIT

Everything is in the commit messages :

 - Use new ProcessUtils::escapeArgument to escape ProcessBuillder prefix
 - Do not throw LogicException in ProcessBuilder::getProcess if no arguments are set but a prefix is

Commits
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1de29b9 [Process] Do not throw LogicException in ProcessBuilder::getProcess if no arguments are set but a prefix is
209799b [Process] Use new ProcessUtils::escapeArgument to escape ProcessBuilder prefix