{cmake} Declare include directories as SYSTEM

[asmaloney]

This allows consumers of the header to ignore all the warnings so -Werror may be used.

See: https://cmake.org/cmake/help/latest/command/target_include_directories.html

(If you would rather I go through and fix the warnings I can work on that. Looks like it's mostly shadowed vars and unused vars in if statements.)

[guybrush77]

Thanks for the pull request. rapidobj includes two third-party libraries, fast_float and earcut. Do you know if the warnings occur in these libraries, in rapidobj code or both?

[asmaloney]

It looks like they are in the rapidobj code.

I'm not getting the warnings locally (Apple Clang), but they show up on CI (13.1.0 on Linux). Using -Wall -Wextra -Wpedantic -Wshadow -Wunused along with several others...

Here are a few:

extern/rapidobj/include/rapidobj/rapidobj.hpp: In lambda function:
extern/rapidobj/include/rapidobj/rapidobj.hpp:6145:49: error: declaration of 'task' shadows a previous local [-Werror=shadow]
 6145 |         if (auto rc = std::visit([](const auto& task) { return task.Execute(); }, task); rc != rapidobj_errc::Success) {
      |                                     ~~~~~~~~~~~~^~~~
extern/rapidobj/include/rapidobj/rapidobj.hpp:6143:21: note: shadowed declaration is here
 6143 |         const auto& task = tasks[fetched_index];
      |                     ^~~~
extern/rapidobj/include/rapidobj/rapidobj.hpp: In function 'rapidobj::Result rapidobj::detail::ParseFile(const std::filesystem::__cxx11::path&, const rapidobj::MaterialLibrary&)':
extern/rapidobj/include/rapidobj/rapidobj.hpp:7133:22: error: unused variable 'string' [-Werror=unused-variable]
 7133 |     } else if (auto* string = std::get_if<std::string_view>(material_library_value)) {
      |                      ^~~~~~
extern/rapidobj/include/rapidobj/rapidobj.hpp:7126:22: error: unused variable 'none' [-Werror=unused-variable]
 7126 |     } else if (auto* none = std::get_if<std::monostate>(material_library_value)) {
      |                      ^~~~
extern/rapidobj/include/rapidobj/rapidobj.hpp:7124:15: error: unused variable 'null' [-Werror=unused-variable]
 7124 |     if (auto* null = std::get_if<std::nullptr_t>(material_library_value)) {
      |               ^~~~
extern/rapidobj/include/rapidobj/rapidobj.hpp: In function 'rapidobj::Result rapidobj::detail::ParseStream(std::istream&, const rapidobj::MaterialLibrary&)':
extern/rapidobj/include/rapidobj/rapidobj.hpp:7214:22: error: unused variable 'string' [-Werror=unused-variable]
 7214 |     } else if (auto* string = std::get_if<std::string_view>(material_library_value)) {
      |                      ^~~~~~
extern/rapidobj/include/rapidobj/rapidobj.hpp:7201:22: error: unused variable 'none' [-Werror=unused-variable]
 7201 |     } else if (auto* none = std::get_if<std::monostate>(material_library_value)) {
      |                      ^~~~
extern/rapidobj/include/rapidobj/rapidobj.hpp:7199:15: error: unused variable 'null' [-Werror=unused-variable]
 7199 |     if (auto* null = std::get_if<std::nullptr_t>(material_library_value)) {
      |               ^~~~
extern/rapidobj/include/rapidobj/rapidobj.hpp: In constructor 'rapidobj::detail::TriangulateTask::TriangulateTask(const rapidobj::Mesh*, rapidobj::Mesh*, size_t, size_t, size_t, size_t, size_t, size_t)':
extern/rapidobj/include/rapidobj/rapidobj.hpp:7268:21: error: declaration of 'size' shadows a member of 'rapidobj::detail::TriangulateTask' [-Werror=shadow]
 7268 |         size_t      size) noexcept
      |         ~~~~~~~~~~~~^~~~
extern/rapidobj/include/rapidobj/rapidobj.hpp:7279:17: note: shadowed declaration is here
 7279 |     size_t      size{};

[guybrush77]

If you don't mind fixing warnings in rapidobj code, that would be great and much appreciated!

We can still merge this PR after the warnings have been fixed.