Sometimes we see errors like this:
criu/cr-restore.gcda:Merge mismatch for function 106

It proabably means that this gcda file was corrupted. According to the
gcc man page, the -fprofile-update=atomic should fix this problem.

v2: this options appered in gcc7, so we need to install it.

Reported-by: Mr Travis CI
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>