Modernise build structure

* Cross-compilable
* Softloadable builds install files in ResourceFS (it looks like this was
  once the case but the feature was dropped at some point). To facillitate
  this, switch component to use the CModule shared makefile
* Consolidate and complete `.gitignore`
* Enable GitLab CI and address issues identified
12 jobs for !6 with CrossCompilationSupport in 19 seconds (queued for 5 seconds)
latest detached
Status Job ID Name Coverage
  Static Analysis
passed #58151
cross
copyright

00:00:00

passed #58142
cross
gitattributes

00:00:01

passed #58143
cross
gitignore

00:00:01

passed #58146
cross
head_log

00:00:01

passed #58149
cross
head_whitesp

00:00:00

passed #58144
cross
license

00:00:01

passed #58148
cross
makefile

00:00:00

passed #58147
cross
merge_log

00:00:01

passed #58150
cross
merge_whitesp

00:00:01

passed #58145
cross
versionnum

00:00:00

 
  Softload
passed #58152
cross
softload

00:00:06

 
  Cleanup
passed #58153
cross
cleanup

00:00:01