Merge topic 'ghs_custom'

2bae6a1346 GHS: Update tests and notes
3b415c60c1 GHS: Update ExternalProject for GHS tools
83c47ef5b8 GHS: Update project layout to accommodate gbuild inconsistencies
5d2e1404bd GHS: Update project layout to build targets correctly
b6bfa7eeb2 GHS: Support add_dependencies() command
39ee9718d9 GHS: Support add_custom_target() command
8d3dad9a76 GHS: Support add_custom_command( OUTPUT ) signature
37acc9e229 GHS: Update custom command build events

Acked-by: Kitware Robot <kwrobot@kitware.com>
Acked-by: Narendhar Manimohan <narendhar15@gmail.com>
Merge-request: !3119