Print CMake messages on stdout rather than stderr

Print CMake messages on stdout rather than stderr

The default version of message("...") print to stderr, which is inappropriate
for informational messages such as the ones we are printing in these cases.

Using message(STATUS "...") makes these messages appear on stdout instead
which is more appropriate.

Change-Id: I02f41e6b4948e6938566f06d7164444bd5b8199e
Signed-off-by: Robert Hughes <robert.hughes@arm.com>