Creates a child process.
argv[0] is the file path of the program to execute, relative to dir. It
is always treated as a file path, even if it does not contain '/'.
pub fn spawnPath(io: Io, dir: Io.Dir, options: SpawnOptions) SpawnError!Child
pub fn spawnPath(io: Io, dir: Io.Dir, options: SpawnOptions) SpawnError!Child {
return io.vtable.processSpawnPath(io.userdata, dir, options);
}