-mno-cygwinでC++のコードをビルドするときは -I/usr/include してはいけない

今日SDLを使ったC++で書かれたゲームのコンパイルをしようとしていたら、wchar関連のエラーが出てコンパイルできないということがあった。

/usr/lib/gcc/i686-pc-mingw32/3.4.4/include/c++/cwchar:146: error: `::fgetwc' has not been declared
/usr/lib/gcc/i686-pc-mingw32/3.4.4/include/c++/cwchar:147: error: `::fgetws' has not been declared
/usr/lib/gcc/i686-pc-mingw32/3.4.4/include/c++/cwchar:148: error: `::fputwc' has not been declared
/usr/lib/gcc/i686-pc-mingw32/3.4.4/include/c++/cwchar:149: error: `::fputws' has not been declared
/usr/lib/gcc/i686-pc-mingw32/3.4.4/include/c++/cwchar:150: error: `::fwide' has not been declared
/usr/lib/gcc/i686-pc-mingw32/3.4.4/include/c++/cwchar:151: error: `::fwprintf' has not been declared
/usr/lib/gcc/i686-pc-mingw32/3.4.4/include/c++/cwchar:152: error: `::fwscanf' has not been declared
/usr/lib/gcc/i686-pc-mingw32/3.4.4/include/c++/cwchar:153: error: `::getwc' has not been declared
/usr/lib/gcc/i686-pc-mingw32/3.4.4/include/c++/cwchar:154: error: `::getwchar' has not been declared
/usr/lib/gcc/i686-pc-mingw32/3.4.4/include/c++/cwchar:159: error: `::putwc' has not been declared
/usr/lib/gcc/i686-pc-mingw32/3.4.4/include/c++/cwchar:160: error: `::putwchar' has not been declared
/usr/lib/gcc/i686-pc-mingw32/3.4.4/include/c++/cwchar:161: error: `::swprintf' has not been declared
/usr/lib/gcc/i686-pc-mingw32/3.4.4/include/c++/cwchar:162: error: `::swscanf' has not been declared
/usr/lib/gcc/i686-pc-mingw32/3.4.4/include/c++/cwchar:163: error: `::ungetwc' has not been declared
/usr/lib/gcc/i686-pc-mingw32/3.4.4/include/c++/cwchar:164: error: `::vfwprintf' has not been declared
/usr/lib/gcc/i686-pc-mingw32/3.4.4/include/c++/cwchar:166: error: `::vfwscanf' has not been declared
/usr/lib/gcc/i686-pc-mingw32/3.4.4/include/c++/cwchar:168: error: `::vswprintf' has not been declared
/usr/lib/gcc/i686-pc-mingw32/3.4.4/include/c++/cwchar:170: error: `::vswscanf' has not been declared
/usr/lib/gcc/i686-pc-mingw32/3.4.4/include/c++/cwchar:172: error: `::vwprintf' has not been declared
/usr/lib/gcc/i686-pc-mingw32/3.4.4/include/c++/cwchar:174: error: `::vwscanf' has not been declared
/usr/lib/gcc/i686-pc-mingw32/3.4.4/include/c++/cwchar:182: error: `::wcsftime' has not been declared
/usr/lib/gcc/i686-pc-mingw32/3.4.4/include/c++/cwchar:189: error: `::wcstod' has not been declared
/usr/lib/gcc/i686-pc-mingw32/3.4.4/include/c++/cwchar:191: error: `::wcstof' has not been declared
/usr/lib/gcc/i686-pc-mingw32/3.4.4/include/c++/cwchar:193: error: `::wcstok' has not been declared
/usr/lib/gcc/i686-pc-mingw32/3.4.4/include/c++/cwchar:194: error: `::wcstol' has not been declared
/usr/lib/gcc/i686-pc-mingw32/3.4.4/include/c++/cwchar:195: error: `::wcstoul' has not been declared
/usr/lib/gcc/i686-pc-mingw32/3.4.4/include/c++/cwchar:196: error: `::wcsxfrm' has not been declared
/usr/lib/gcc/i686-pc-mingw32/3.4.4/include/c++/cwchar:202: error: `::wprintf' has not been declared
/usr/lib/gcc/i686-pc-mingw32/3.4.4/include/c++/cwchar:203: error: `::wscanf' has not been declared
/usr/lib/gcc/i686-pc-mingw32/3.4.4/include/c++/cwchar:249: error: `::wcstold' has not been declared
/usr/lib/gcc/i686-pc-mingw32/3.4.4/include/c++/cwchar:258: error: `::wcstoll' has not been declared
/usr/lib/gcc/i686-pc-mingw32/3.4.4/include/c++/cwchar:259: error: `::wcstoull' has not been declared
/usr/lib/gcc/i686-pc-mingw32/3.4.4/include/c++/cwchar:265: error: `__gnu_cxx::wcstold' has not been declared

こんな感じのが大量に出る。

結論からいうと、 http://flightgear.jpn.org/modules/d3forum/index.php?post_id=1628 に書かれている通りで、 -I/usr/include していたのが原因だった。