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)
11 jobs for master in 51 seconds (queued for 4 seconds)
Status Job ID Name Coverage
  Static Analysis
passed #54810
cross
copyright

00:00:01

passed #54803
cross
gitattributes

00:00:00

passed #54804
cross
gitignore

00:00:01

passed #54807
cross
head_log

00:00:00

passed #54809
cross
head_whitesp

00:00:00

passed #54805
cross
license

00:00:00

passed #54808
cross
makefile

00:00:00

passed #54806
cross
versionnum

00:00:00

 
  Softload
passed #54811
cross
softload

00:00:28

 
  Deploy
passed #54812
cross
deploy_to_runner

00:00:14

 
  Cleanup
passed #54813
cross
cleanup

00:00:01