Add gitlab CI config

1 job for master in 1 minute and 9 seconds
Status Job ID Name Coverage
  Test
failed #165
build

00:01:09

 
Name Stage Failure
failed
build Test There is an unknown failure, please try again
$ g++ --version
g++ (Debian 4.9.2-10) 4.9.2
Copyright (C) 2014 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ ./example
/bin/bash: line 56: ./example: No such file or directory
ERROR: Job failed: exit code 1