FR: Make handling of _<CONFIG> suffix of variables and properties case insensitive
I've spent more time than I'd like to admit not understanding why CMAKE_INTERPROCEDURAL_OPTIMIZATION_Release isn't working, only to eventually find out I need to use CMAKE_INTERPROCEDURAL_OPTIMIZATION_RELEASE (tested with both Xcode and Ninja Multi-Config generators on macOS).
I find this surprising given that the default configuration name is Release, not RELEASE; but rather than debating that, I think the best improvement, helping others to avoid this gotcha in the future, would be to just make the <_CONFIG> suffix part of configuration variables and properties case-insensitive. I realize variables (and properties?) are case-sensitive, but the code testing for the presence of such configuration could be made case-insensitive (with some arbitrary handling for the edge-case of multiple definitions with different cases).
The only concern, I guess, would be breaking projects with multiple configurations having the same spelling with different case. To me that seems a very minor concern, though, and my guess is such projects are already prone to issues, e.g., given the topic of this issue.