Conflicts between system and libc++ headers

[alandefreitas]

This error happened in https://github.com/cppalliance/ws_proto/actions/runs/11892602095/job/33135815935?pr=3#step:10:434

In file included from D:\a\ws_proto\ws_proto\boost-root\libs\url\extra\test_main.cpp:25:
In file included from C:\Program Files (x86)\Windows Kits\10\Include\10.0.26100.0\ucrt\crtdbg.h:13:
In file included from C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Tools\MSVC\14.42.34433\include\vcruntime_new_debug.h:10:
C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Tools\MSVC\14.42.34433\include\vcruntime_new.h:27:33: error: redefinition of 'align_val_t'
   27 |     _VCRT_EXPORT_STD enum class align_val_t : size_t {};
      |                                 ^
C:\Users\runneradmin\AppData\Roaming\antora\Caches\reference-collector\mrdocs\win32\develop\share\mrdocs\libcxx\new:181:12: note: previous definition is here
  181 | enum class align_val_t : size_t {};
      |            ^
In file included from D:\a\ws_proto\ws_proto\boost-root\libs\url\extra\test_main.cpp:25:
In file included from C:\Program Files (x86)\Windows Kits\10\Include\10.0.26100.0\ucrt\crtdbg.h:13:
In file included from C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Tools\MSVC\14.42.34[433](https://github.com/cppalliance/ws_proto/actions/runs/11892602095/job/33135815935?pr=3#step:10:434)\include\vcruntime_new_debug.h:10:
C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Tools\MSVC\14.42.34433\include\vcruntime_new.h:35:33: error: redefinition of 'nothrow_t'
   35 |         _VCRT_EXPORT_STD struct nothrow_t {
      |                                 ^

It seems like the bundled Libc++ headers are included because system-includes is false, but the system headers are also included because they're in the compile_commands.json file and are not being removed. This leads to redefinition errors.

Although I'm not completely sure this is what's causing the issue because these different headers would still need to be included in the code and the error doesn't show a stacktrace of includes.