D: How do I pipe (|) through three programs using std.process?

[BoQsc]

Using `spawnShell` it all seem to work.

However the question of why `spawnProcess(["find", "string to 
find"]` is not working and produces error is still unresolved.


Works with `spawnShell`:
```
import std.stdio;
import std.process;

version (Windows) { enum Find = "find"; }
version (Posix) { enum Find = "grep"; }

int main (string [] args)
{
    auto p1 = pipe;
    auto p2 = pipe;

    auto pid1 = spawnShell("echo HelloWorld", stdin, p1.writeEnd);
    auto pid2 = spawnShell("find  \"HelloWorld\"", p1.readEnd, 
p2.writeEnd);
    auto pid3 = spawnShell("find  \"HelloWorld\"", p2.readEnd, 
stdout);

    wait (pid1);
    wait (pid2);
    wait (pid3);
    return 0;
}
```