major: Switch to forward slashes(+more) to fix compilation on Linux (#1403)

Notably also adds some metadata files for NixOS 

* add support for linux clang cross compiles

* add linux clang instructions

* un-capitalize Mob.horse.*

* update the description in flake.nix

---------

Co-authored-by: Loki <lokirautio@gmail.com>

Minecraft.Client/Xbox/MinecraftWindows.rc

@@ -1,6 +1,6 @@
 // Microsoft Visual C++ generated resource script.
 //
-#include "resource.h"
+#include "Resource.h"
 
 #define APSTUDIO_READONLY_SYMBOLS
 /////////////////////////////////////////////////////////////////////////////
@@ -126,7 +126,7 @@ END
 
 1 TEXTINCLUDE 
 BEGIN
-    "resource.h\0"
+    "Resource.h\0"
 END
 
 2 TEXTINCLUDE