sanitycheck: add --log-file to log everything to a file too

Currently CI plays tricks with `tee` to capture the output and post
process it. This makes it more complex to handle and easier for it to
fail in ways it should not.

So add a simple log capture option sanity check that mirrors the
stdout output, removing color encoding for errors.

Change-Id: I6de0b6cfe4da9c289f537979545dddbcd49cf834
Signed-off-by: Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>