scripts/install-buildtools: Update to 3.2 M1 buildtools

This fixes issues with openssl certs not working properly which meant error
reporting to an error report server was failing.

Also, all our downloads are now standarised on "sha256sum" so adjust for that.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit bc8b44e1)
Signed-off-by: Steve Sakoman <steve@sakoman.com>