update zig's bundled mingw-w64 libc to support older Windows versions

[dr3murr]

zig cc produces binaries requiring a Windows version of at least 6.0 (Vista).
mingw32 builds binaries that run perfectly well on my Windows 95 box, so this is probably a regression somewhere.

[daurnimator]

What are you passing as the target? See #1907 (comment)

[andrewrk]

Here is the process for how mingw-w64 is configured: https://github.com/ziglang/zig/wiki/Updating-libc#mingw-w64-windows

We currently pass --with-default-win32-winnt=0x0603.

[zu3st]

What are you passing as the target? See #1907 (comment)

Running zig cc hello.c -target i386-windows.xp-gnu results in the PE's subsystem version header being set to 6, consequently the output cannot be run on Windows XP.

After bytepatching the subsystem version header from 6 to 4, the program runs just fine.

dumpbin excerpt:

OPTIONAL HEADER VALUES
  6.00 operating system version
  0.00 image version
  6.00 subsystem version
  0 Win32 version

[sskras]

@andrewrk commented Apr 6, 2020:

Here is the process for how mingw-w64 is configured: https://github.com/ziglang/zig/wiki/Updating-libc#mingw-w64-windows

We currently pass --with-default-win32-winnt=0x0603.

The larger excerpt:

rm -rf $ZIGSRC/lib/libc/include/any-windows-any
cd mingw-w64-headers
./configure --prefix=/tmp/prefix --with-default-win32-winnt=0x0603
make install
mv /tmp/prefix/include $ZIGSRC/lib/libc/include/any-windows-any

...
Next, update all the files in lib/libc/mingw/*.

Does it mean that mingw-w64 needs to be reconfigured / rebuilt before building binaries for Windows XP / Server 2003 / ReactOS using zig cc?