C#: Initial NativeAOT support

This commit adds initial support for games exported as NativeAOT shared
libraries.

At this moment, the NativeAOT runtime is experimental. Additionally,
Godot is not trim-safe as it still makes some use of reflection.
For the time being, a rd.xml file is needed to prevent code triming:

```
<Directives xmlns="http://schemas.microsoft.com/netfx/2013/01/metadata">
  <Application>
    <Assembly Name="GodotSharp" Dynamic="Required All" />
    <Assembly Name="GAME_ASSEMBLY" Dynamic="Required All" />
  </Application>
</Directives>
```

These are the csproj changes for publishing:

```
  <PropertyGroup>
    <NativeLib>Shared</NativeLib>
  </PropertyGroup>
  <ItemGroup>
    <RdXmlFile Include="rd.xml" />
    <PackageReference Include="Microsoft.DotNet.ILCompiler" Version="7.0.0-*" />
  </ItemGroup>
```

More info:
- https://github.com/dotnet/runtimelab/blob/feature/NativeAOT/docs/using-nativeaot/compiling.md
- https://github.com/dotnet/runtimelab/tree/feature/NativeAOT/samples/NativeLibrary
- https://github.com/dotnet/runtimelab/blob/feature/NativeAOT/docs/using-nativeaot/rd-xml-format.md

1 files changed, 1 insertions, 0 deletions

diff --git a/modules/mono/mono_gd/gd_mono.h b/modules/mono/mono_gd/gd_mono.h
index 66ed331b67..301782575c 100644
--- a/modules/mono/mono_gd/gd_mono.h
+++ b/modules/mono/mono_gd/gd_mono.h
@@ -61,6 +61,7 @@ class GDMono {
 	bool finalizing_scripts_domain;
 
 	void *hostfxr_dll_handle = nullptr;
+	bool is_native_aot = false;
 
 #ifdef TOOLS_ENABLED
 	bool _load_project_assembly();