Use ln -n instead of -h to allow building the kernel on Linux

[arichardson]

Summary

Both flags do the same thing but -n is more widely understood.

[emaste]

LGTM. I wonder if we should have a tiny comment that says we use -n for broader portability (since the -h is documented in the man page as the canonical option).

Or maybe we could add Portable scripts may wish to use -n instead of -h . to the -n description in ln's manpage?

[jhb]

Possibly s/understood/supported/ in the commit message, but that's a minor nit.