C++: Improve error message when finding X11 macro `Unsorted` #13825

Job	Run time
cpp-paths-filter	5s
docs-paths-filter	5s
python-paths-filter	4s
rust-paths-filter	4s
web-paths-filter	4s
Checks / Rerun lints	29s
Checks / Check if running codegen would produce any changes	1m 22s
Checks / Lint markdown	23s
Checks / Spell Check	5s
Checks / Check links	19s
Checks / Misc formatting	15s
Update PR Body / Update PR body	23s
Deploy Landing Preview	0s
Rust Checks	0s
Build rerun_js	0s
Build web viewer	0s
C++ tests / matrix_prep	6s
C++ tests / C++ formatting check	4m 8s
Upload Web	0s
Save PR Summary	0s
Minimum CLI Build	0s
Python Checks	0s
Minimum Wheel Build	0s
Minimum Wheel Test	0s
C++ tests / C++ build & test - Linux x64, C++17	3m 51s
C++ tests / C++ build & test - Linux x64, C++20	3m 49s
C++ tests / C++ build & test - Windows x64	10m 28s
C++ tests / C++ build & test - Mac aarch64	6m 38s
	32m 38s

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