Update .gitlab-ci.yml

1 job for master in 18 seconds (queued for 14 minutes and 49 seconds)
Name Stage Failure
build Build

-- Configuring incomplete, errors occurred!
See also "/builds/gaussier/drone_flyMonitor2/Com_server/build/CMakeFiles/CMakeOutput.log".
make[1]: Entering directory '/builds/gaussier/drone_flyMonitor2/Com_server/build'
make[1]: Leaving directory '/builds/gaussier/drone_flyMonitor2/Com_server/build'
make[1]: *** No targets specified and no makefile found. Stop.
Makefile:6: recipe for target 'flyMonitor' failed
make: *** [flyMonitor] Error 2
ERROR: Job failed: exit code 1