Compile Gtk# 2.99.3 in Cygwin unknown types uid_t

问题:

After compiling last version of mono in Cygwin64 (last version)
I compiled some C# tests with the mono c# compiler (msc)

I want to make some tests with Gtk
so I downloaded the source code and try to compile...

after solving some minor issues that were constantly stopping the compilation
I become stuck with the error of 2 unknown types:

uid_t
pid_t

the errors are:

/usr/include/glib-2.0/gio/gcredentials.h:75:1: error: unknown type name 'uid_t'
/usr/include/glib-2.0/gio/gcredentials.h:79:52: error: unknown type name 'uid_t'

already verified the installation of all mingw*/gcc* libraries also all *-devel and *-debug packages but no luck...

any ideas ?