Currently, Mbed TLS can be built with make, and we rely on this in many
`all.sh` components. Mbed TLS knows how to build TF-PSA-Crypto, but this
changes from time to time, and it's hard to do the necessary changes in both
repositories at the same time.
Create a file that Mbed TLS can consume to find out some information needed
to build TF-PSA-Crypto, such as the locations of various files.
Create this file in Mbed TLS. Once we have finished moving code to it, the
file will move to TF-PSA-Crypto.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>