Add --verbose parameter to symlink_project.php, and a variable turn on verbose

Migrated issue

Reported by: jonathan1055

Related to !413 (merged)

Problem/Motivation

Several of our internal scripts have a --verbose parameter. This needs to be hardcoded in the template if you want to use it, then removed when finished. In #3546508: Add recipes path handling @fjgarlin suggested we have a new environment variable to allow the verbose parameter to be set easily, either via the variable in the job (for use in downstream testing) or via the pipeline UI form.

In addition, the script symlink_project.php needs to have a verbose parameter, to enable debugging particularly during the changes for Recipes.

Proposed resolution

• Add environment variable SCRIPT_VERBOSE, default 0, set to 1 to use --verbose in all scripts that support it
• Add verbose parameter and debug output to symlink_project.php