MINGW-packages: Compiler does not find pty.h

I’m trying to compile a graphical terminal for msys2/mingw64. I thought pangoterm might be a good place to start (http://www.leonerd.org.uk/code/pangoterm/)

I installed msys2-devel and the other mentioned packages from https://github.com/msys2/msys2/wiki/Contributing-to-MSYS2

I cloned the MINGW-packages repo and installed libvterm-bzr

Now when compiling pangoterm it complains it can’t find pty.h but the file is there in /usr/include, and for some reason it’s not part of the gcc include path, which is:

$ echo | gcc -E -Wp,-v -
# 1 "<stdin>"
# 1 "<built-in>"
# 1 "<command-line>"
# 1 "<stdin>"
ignoring duplicate directory "C:/msys/mingw64/lib/gcc/../../lib/gcc/x86_64-w64-mingw32/6.3.0/include"
ignoring nonexistent directory "C:/building/msys64/mingw64/include"
ignoring nonexistent directory "/mingw64/include"
ignoring duplicate directory "C:/msys/mingw64/lib/gcc/../../lib/gcc/x86_64-w64-mingw32/6.3.0/include-fixed"
ignoring duplicate directory "C:/msys/mingw64/lib/gcc/../../lib/gcc/x86_64-w64-mingw32/6.3.0/../../../../x86_64-w64-mingw32/include"
ignoring nonexistent directory "C:/building/msys64/mingw64/x86_64-w64-mingw32/include"
#include "..." search starts here:
#include <...> search starts here:
 C:/msys/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/6.3.0/include
 C:/msys/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/6.3.0/../../../../include
 C:/msys/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/6.3.0/include-fixed
 C:/msys/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/6.3.0/../../../../x86_64-w64-mingw32/include
End of search list.

When I add the /usr/include path to the CCFLAGS I get a lot of duplicate includes, so I guess that isn’t the answer.

I’m running the commands from a MSYS2 64-bit mintty shell.

I guess I’m running into a very noobish error, could you help me figure out what the problem might be?