cppcheckexecutor.cpp: extracted platform-dependent code into separate files

[firewave]

This only refactors the code and does not functional changes.

There's also some bugs/missing features I could have tackled but I will do that in a separate PR.

The goal is to have tests for this code since it might require changes to properly resolve https://trac.cppcheck.net/ticket/11255.

[firewave]

All these Makefile and dmake changes really highlight that still using make and Visual Studio projects is quite an inconvenience with the extra effort required. Especially with both of them just providing a subset of what CMake is offering.

[firewave]

All these Makefile and dmake changes really highlight that still using make and Visual Studio projects is quite an inconvenience with the extra effort required. Especially with both of them just providing a subset of what CMake is offering.

I do have an easy approach to update *.vcxproj files via dmake though.