Use patched FakeIt

The upstream version is not compatible with Clang >=19 so it breaks
macOS builds on latest agents. Added readme that describes what's the
deal.

fakeit.hpp has to be added to .codespellrc explicitly because codespell
actually can't properly ignore folders from .codespellrc when called
from pre-commit. See codespell-project/codespell#3196

Author: MiKom

.codespellrc

@@ -1,5 +1,5 @@
 [codespell]
-skip = ./build-*,.git
+skip = ./build*,.git,*fakeit.hpp
 interactive = 3
 #ignore camelCase, regardless. also mixed case words with correct spelling
 ignore-regex = \b([a-z]+[A-Z0-9][a-z0-9]*|te|fo)\b

3rdparty/.clang-format

@@ -0,0 +1 @@
+DisableFormat: true

3rdparty/fakeit/README.md

@@ -0,0 +1,18 @@
+# FakeIt
+
+FakeIt 2.4.1 (from <https://raw.githubusercontent.com/eranpeer/FakeIt/refs/tags/2.4.1/single_header/doctest/fakeit.hpp>)
+with a fix for stricter compilation on Clang >=19.
+
+Line 7924 changed from:
+
+```cpp
+ParamWalker<N - 1>::template Assign(arg_vals, std::forward<arglist>(args)...);
+```
+
+```cpp
+ParamWalker<N - 1>::Assign(arg_vals, std::forward<arglist>(args)...);
+```
+
+See <https://github.com/eranpeer/FakeIt/issues/348>
+
+After FakeIt 2.5.0 is released we can go back to using the vanilla version.