Check toolchain license prior to initial CMake invocation

[jkrech]

Describe The Problem To Be Solved
Duplicated from here: ARM-software/vscode-cmsis-csolution#478

If cmake invokes a UBL license protected compiler toolchain and the license check fails or runs in a time-out the user experience is bad, as it is not immediately obvious what went wrong.

There a number of scenarios for a failed license:
a) license activation failed or ignored by user
b) the license cache expired and the license server is not reachable (e.g. outside of the company network)

-- Check for working C compiler: /home/codespace/.vcpkg/artifacts/2139c4c6/compilers.arm.armclang/6.24.0/bin/armclang
-- Check for working C compiler: /home/codespace/.vcpkg/artifacts/2139c4c6/compilers.arm.armclang/6.24.0/bin/armclang - broken
-- Configuring incomplete, errors occurred!

-- stderr output is:
CMake Error at /home/codespace/.vcpkg/artifacts/2139c4c6/tools.kitware.cmake/3.31.5/share/cmake-3.31/Modules/CMakeTestCCompiler.cmake:67 (message):
  The C compiler

    "/home/codespace/.vcpkg/artifacts/2139c4c6/compilers.arm.armclang/6.24.0/bin/armclang"

  is not able to compile a simple test program.

  It fails with the following output:

    Change Dir: '/workspaces/vscode-get-started/tmp/1/CMakeFiles/CMakeScratch/TryCompile-RQkBpB'

(Optional): Suggest A Solution
In cbuild we could check whether armclang is "operational" before kicking off cmake.

Step one: check the active toolchain of the active target-set.

In case of AC6 already a version check failing in case of problems with the license

armclang --version
armclang: error: Failed to check out a license.

If it fails we print an error instead of starting cmake. In VS Code the build button and related commands could be disabled.

We could also implement that in cbuild
A concise description of your preferred solution. Things to address include:

• Details of the technical implementation
• Tradeoffs made in design decisions
• Caveats and considerations for the future

If there are multiple solutions, please present each one separately. Save comparisons for the very end.