[Gpg4win-users-en] building for Win32: can't find windows.h

[sweepslate]

I'm having trouble making Win32 build of GnuPG2 in a Linux host.

I'm running Slackware which comes with gnupg2-2.0.17. I choose to use 
the source from this version since I already have all the dependencies 
(if I manage to make one build right, I can upgrade everything later).

I did a './configure --build=mingw32' and then 'make', but I got this error:

--- snip ---
make[3]: Leaving directory `/home/user/temp/slack-gpg2/gnupg-2.0.17/gl'
make[2]: Leaving directory `/home/user/temp/slack-gpg2/gnupg-2.0.17/gl'
Making all in include
make[2]: Entering directory 
`/home/user/temp/slack-gpg2/gnupg-2.0.17/include'
make[2]: Nothing to be done for `all'.
make[2]: Leaving directory `/home/user/temp/slack-gpg2/gnupg-2.0.17/include'
Making all in jnlib
make[2]: Entering directory `/home/user/temp/slack-gpg2/gnupg-2.0.17/jnlib'
gcc -DHAVE_CONFIG_H -I. -I..  -I../intl  -DJNLIB_IN_JNLIB  -g -O2 -Wall 
-Wno-pointer-sign -Wpointer-arith -MT stringhelp.o -MD -MP -MF 
.deps/stringhelp.Tpo -c -o stringhelp.o stringhelp.c
stringhelp.c:33:22: fatal error: windows.h: No such file or directory
compilation terminated.
make[2]: *** [stringhelp.o] Error 1
make[2]: Leaving directory `/home/user/temp/slack-gpg2/gnupg-2.0.17/jnlib'
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory `/home/user/temp/slack-gpg2/gnupg-2.0.17'
make: *** [all] Error 2
user at darkstar:~/temp/slack-gpg2/gnupg-2.0.17$
--- snip ---

It can't find windows.h. Neither do I. Any ideas?