Mbed TLS development no longer has a root makefile. Checking it resulted
in the following on stderr:

head: cannot open 'Makefile' for reading: No such file or directory

and indeed the function was no longer working as intended.

Signed-off-by: Manuel Pégourié-Gonnard <[email protected]>

In a successful run, it had absolutely no visible effect. The output
even included cmake's output (see next commit).

It only had an effect in case errors are found: then they are reported
in a terse way (one line per error) instead of with full context and
explanations.

As a user, I expect a script invoked with -q to not have 10 lines of
output telling me "i'm checking this... it's ok... that too is ok, etc"
(And, see next-next commit, I definitely don't expect the list of all
things that are OK to be printed on stderr...)

Signed-off-by: Manuel Pégourié-Gonnard <[email protected]>

So far it was already present even with -q. Clearly we don't want it
with -q, and I'd argue in normal usage we don't care either, it really
is an internal detail.

Signed-off-by: Manuel Pégourié-Gonnard <[email protected]>

Before this commit, upon success the script was writing nothing to
stdout (except output from cmake before the previous commit) and
everything to stderr.

This is not normal behaviour. It confuses scripts like `all.sh` that try
to implemented their own quiet mode by by redirecting stdout of
components to /dev/null. It would confuse scripts which would redirect
stderr to a file then look if this file is empty or not to double-check
for issues (in addition to looking at the script's exite code).

Instead, use stdout for normal output (no options) and debug output
(-v), and use stderr for warnings and errors.

Signed-off-by: Manuel Pégourié-Gonnard <[email protected]>