when compiling on Ubuntu

[aballant]

Hi,

I get..., I don't get this issue on Darwin/MacOS

remote: /build/app/Packages/Spawn-0.0.3/Sources/Spawn/Spawn.swift:87:35: error: cannot convert value of type '(UnsafeMutableRawPointer) -> UnsafeMutableRawPointer?' to expected argument type '@convention(c) (UnsafeMutableRawPointer?) -> UnsafeMutableRawPointer?'
remote: pthread_create(&tid, nil, callback, &threadInfo)
remote: ^~~~~~~~
remote: as! @convention(c) (UnsafeMutableRawPointer?) -> UnsafeMutableRawPointer?
remote: /build/app/Packages/Spawn-0.0.3/Sources/Spawn/Spawn.swift:93:12: error: initializer for conditional binding must have Optional type, not 'pthread_t' (aka 'UInt')
remote: if let tid = tid {