Enable GitLab CI/CD

Detail:
* Enable GitLab CI
* Address issues identified by CI jobs, excluding those related to cppcheck
* Enable GitLab CD for stubs (used implicitly when linker is invoked by cc)
12 jobs for !5 with CrossCompilationSupport in 37 seconds (queued for 53 seconds)
detached
Status Job ID Name Coverage
  Static Analysis
passed #53623
cross
copyright

00:00:01

passed #53614
cross
gitattributes

00:00:01

passed #53615
cross
gitignore

00:00:00

passed #53618
cross
head_log

00:00:00

passed #53621
cross
head_whitesp

00:00:00

passed #53616
cross
license

00:00:00

passed #53620
cross
makefile

00:00:00

passed #53619
cross
merge_log

00:00:00

passed #53622
cross
merge_whitesp

00:00:00

passed #53617
cross
versionnum

00:00:00

 
  Softload
passed #53624
cross
softload

00:00:27

 
  Cleanup
passed #53625
cross
cleanup

00:00:00