GDC MINGW BUILD: version (Windows) NOT DEFINED

[MINGW-USER]

It seems version (Windows) is not defined into the compiler 
gdc.exe
gdc (GCC) 9.0.0 20181221 (experimental)
built with msys2/mingw-w64 on Windows 10.

The trouble appears while building libdruntime

EXAMPLE: libphobos\libdruntime\core\stdc\time.d
error: undefined identifier 'time_t'
error: undefined identifier 'tm'

Manually add

version (GNU) {
     alias c_long time_t;
     alias c_long clock_t;
}

into time.d then it compiles but it seems weird.

The trouble is that there are many other similar errors
with core\stdc\stddef.d, stdlib.d, stdint.d, etc ...

Help needed.