[Bug 46293] New: winegcc: stdlib.h and math.h not found when including C++ 's <cstdlib> or <cmath>

https://bugs.winehq.org/show_bug.cgi?id=46293

Bug ID: 46293
           Summary: winegcc: stdlib.h and math.h not found when including
                    C++'s <cstdlib> or <cmath>
           Product: Wine
           Version: 3.21
          Hardware: x86
               URL: https://forum.cockos.com/showthread.php?p=2070238#post
                    2070238
                OS: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: tools
          Assignee: [e-mail]
          Reporter: [e-mail]
   Regression SHA1: 0e279d26b8386fc878f17bd6768e46e1cf9c5128
      Distribution: ArchLinux

Created attachment 63015
  --> https://bugs.winehq.org/attachment.cgi?id=63015
wineg++ -v test.cpp

<cstdlib> and <cmath> of the C++ standard library fail to find <stdlib.h> and
<math.h> (with #include_next) when using wineg++ since Wine 3.21.

This seems to be because wineg++ (built with --prefix=/usr) now adds -isystem
/usr/include to GCC's command line. This changes the order directories are
searched (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70129).