| targetGuid | The GUID of the target, such as the one returned by GetUnityFrameworkTargetGuid. |
| name | The name of the phase. |
| dstPath | The destination path. |
| subfolderSpec | The "subfolder spec". The following usages are known: "10" for embedding frameworks; "13" for embedding app extension content; "16" for embedding watch content. |
string Returns the GUID of the new phase.
Creates a new copy files build phase for a given target.
If a copy files build phase with the same name, `dstPath`, and `subfolderSpec` is already configured for the target, the function returns the existing phase. The new phase is placed right before Unity's post-process placeholder target (if it exists).