Incorrect api used for sys_read_dir on windows

[tobil4sk]

On windows, neko uses FindFirstFileA for sys_read_dir. This returns ANSI encoded strings (not to be confused with ASCII) which means that any non-ascii characters are not compatible with utf8, so they can cause issues when the strings from this function are passed to other places.

We should instead use the FindFirstFileW variant which gives utf-16 encoded strings, which can then be converted to valid utf-8.

Similarly, we should replace any use of ANSI variants of the windows api.

This way the behaviour will match non-windows platforms and be more compatible.

[tobil4sk]

Another potential fix for this is to set utf-8 in the manifest of neko.exe: https://learn.microsoft.com/en-us/windows/apps/design/globalizing/use-utf8-code-page

Until recently, Windows has emphasized "Unicode" -W variants over -A APIs. However, recent releases have used the ANSI code page and -A APIs as a means to introduce UTF-8 support to apps. If the ANSI code page is configured for UTF-8, then -A APIs typically operate in UTF-8. This model has the benefit of supporting existing code built with -A APIs without any code changes.

(Though, I think this page is quite old.)

It is a fairly easy change in cmake, I was even able to apply it to an existing neko executable using mt.exe. The downside is that it won't be applied automatically to programs generated using nekotools boot -c (not sure about regular nekotools boot), and that if users have ndlls that rely on legacy windows ansi code pages then those will break.

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestVersion="1.0">
  <trustInfo xmlns="urn:schemas-microsoft-com:asm.v3">
    <security>
      <requestedPrivileges>
        <requestedExecutionLevel level="asInvoker" uiAccess="false"></requestedExecutionLevel>
      </requestedPrivileges>
    </security>
  </trustInfo>
  <application xmlns="urn:schemas-microsoft-com:asm.v3">
    <windowsSettings>
      <activeCodePage xmlns="http://schemas.microsoft.com/SMI/2019/WindowsSettings">UTF-8</activeCodePage>
    </windowsSettings>
  </application>
</assembly>