Change how CMake generates version files

[alef]

Summary

Build "Change how CMake generates version files"

Purpose of change

I've found the version.cmake was a duplicate of what done at configuration time.

Describe the solution

✅ Moved version.h and VERSION.txt generation into version.cmake.
✅ Only revwrite version.h if the version found by git is different. This is how Makefile does it
✅ In src/, use CMAKE_CURRENT_SOURCE_DIR instead of CMAKE_SOURCE_DIR/src because why not

Describe alternatives you've considered

❌ Oddly thought that making getVersionString() constexpr would have been different then a preprocessor macro 🤦‍♂️ ...

Testing

✅ Visual Studio CMake preset build
✅ MSVC Command line CMake preset build
✅ Ubuntu WSL2 command line CMake preset build

Additional context

None

[andrei8l]

This broke source releases that now get HEAD-HASH-dirty (and some log spam) as their version instead of the fallback 0.I, when built with cmake. Why was this change needed anyway?