Patch Phing to fix relative symlinks

[byrond]

Description

• Fixes issues discovered in Automatically run drush inside of ddev #174.
• Patches Phing to fix support for relative symlinks (according to Relative symlinks phingofficial/phing#695, which was only added to Phing 3).
• Uses a relative symlink for the_build_utility module, so it will be correct inside the DDEV container when created outside.
• Updates IncludeResourceTask to use SymlinkTask in order to take advantage of required relative symlinks.

This also requires adding cweagans/composer-patches and the following line to composer.json, so the skeleton will need to be updated:

"extra": {
    "enable-patching": true
}

Testing instructions

• Create a new project using Composer, or use an existing one. Backup your database if using an existing project, and you want to keep it.
• composer require cweagans/composer-patches
• Add "enable-patching": true to the "extra": { } section of composer.json
• Change the version of The Build in composer.json to "palantirnet/the-build": "dev-detect-ddev-byron".
• composer update palantirnet/the-build (You should see Composer remove Phing, reinstall it, and add the patch.)
• ddev start (if the project isn't already running)
• ddev drush sql-drop
• vendor/bin/the-build-installer
• Use defaults (or settings that match your existing project). Choose to install Drupal when prompted.

[becw]

This should be protected instead of private I think?

[becw]

I went ahead and made this change.

[becw]

Can we add a README to the patches directory that explains where this patch comes from?

[becw]

I went ahead and added a README.

[becw]

I had two comments/change requests but otherwise this looks good.