stubom: newlib: Enable C99 formats for %z

stubom: newlib: Enable C99 formats for %z

vtpmmgr was changed to print size_t with the %z modifier, but newlib
isn't compiled with %z support.  So you get output like:

root seal: zu; sector of 13: zu
root: zu v=zu
itree: 36; sector of 112: zu
group: zu v=zu id=zu md=zu
group seal: zu; 5 in parent: zu; sector of 13: zu
vtpm: zu+zu; sector of 48: zu

Enable the C99 formats in newlib so vtpmmgr prints the numeric values.

Fixes: 9379af08ccc0 ("stubdom: vtpmmgr: Correctly format size_t with %z when printing.")
Signed-off-by: Jason Andryuk <jandryuk@gmail.com>
Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Reviewed-by: Daniel P. Smith <dpsmith@apertussolutions.com>