Change the warnings to errors and stop build process

[ReinhardKeil]

Describe the bug

These messages are currently classified as warning:

> cbuild CubeMX_Basic_solution\CubeMX.csolution.yml --context-set
warning csolution: unknown access sequence: 'LinkerRegionsHeader'
CubeMX_Basic_solution/$LinkerRegionsHeader$ - warning csolution: specified regions header was not found
CubeMX_Basic_solution/$LinkerRegionsHeader$ - warning csolution: specified regions header was not found
CubeMX_Basic_solution/$LinkerRegionsHeader$ - warning csolution: specified regions header was not found

The build process does therefore not stop and it finally fails in the linker step (with a cryptic error) as the regions header was not found. As a user you are focusing on the error (not the warning) and it is very hard to spot the underlying problem.

To Reproduce

Use example from #1813

Change the variable "LinkerRegionsHeader" in csolution.yml (mimic a typo).

Expected behavior

Change this messages to type error:

warning csolution: unknown access sequence: 'LinkerRegionsHeader'
CubeMX_Basic_solution/$LinkerRegionsHeader$ - warning csolution: specified regions header was not found

The build process should stop (no CMake call).

Side note: why is warning csolution: specified regions header was not found shown 3 times?

Environment:

• CMSIS-Toolbox 2.6.1
• OS: Windows