System include path extraction only works in English

[oin]

I was trying to make cquery work on a Windows project that I work on on macOS 10.14, using the i686-w64-mingw32 toolchain. Although cquery successfully invoked the compiler with the appropriate flags to make it list system include paths, it didn't parse any of it.

Looking at the code for the system include extractor made it clear what happened: as my system is in French, the extractor couldn't see "#include <...> search starts here:" (it's "la recherche pour #include <...> débute ici:" on my system).
Running cquery with the LC_ALL environment variable set to C corrected the issue (still not able to use cquery with mingw, but that's another story). Maybe this could be included somewhere in the documentation, or the environment variable could be forced?

https://github.com/cquery-project/cquery/blob/518d7798a375ba90d13093723325a6ca25439312/src/clang_system_include_extractor.cc#L43