Dead lock when PBXObjects.delete

[antscript]

Call xcodeProj.pbxproj.delete(object: ) lead to dead lock.

solve:
add

defer {
    lock.unlock()
}

to PBXObjects.swift in func delete(reference: ) after lock.lock().

[pepicrft]

Thanks for reporting this @antscript. Feel free to open a PR with the fix that you suggested. Otherwise, we can look into it.