tfm_builder.py: Do not check the presence of optional artifacts

With the introduction of multiple image boot the names of certain
binaries depend on the number of updateable images (and they may not
even exist). CI should not check the presence of these build artifacts.

Change-Id: I615fe773bda10c1794284fd492c99ac099b09a08
Signed-off-by: David Vincze <david.vincze@arm.com>
1 file changed