child process cannot resolve binaries via PATH with tilde character

Given a path environment variable: `PATH="/usr/bin:/usr/local/bin:~/bin,`child_process` is not able to resolve the path of the binary when with tilde expression is used. It would be great to have support for this, making the behavior like is usual in POSIX platforms. Probably this is a specific behavior in `bourne shell`, but it's very generalized actually.