Remove Microsoft.DotNet.CilStrip.Sources from runtime-assets

[ViktorHofer]

https://github.com/dotnet/runtime-assets/blob/main/src/Microsoft.DotNet.CilStrip.Sources/README.md mentions that Microsoft.DotNet.CilStrip.Sources is a temporary copy and will be replaced during .NET 7.

Can these sources now be removed from the repository?

cc @steveisok

[steveisok]

@akoeplinger @fanyang-mono I think the readme should at least be updated. Do you think we can have an ILStrip replacement in .NET 9?

[fanyang-mono]

If the functionality of writing a modified assembly to file and validating the new assembly are implemented, then probably yes.

[lewing]

what is the status here?

[steveisok]

This one is tough because modern cecil rewrites tokens and aot images rely on exact values. Here's what I see our options are in .NET 9:

1. An API like Efficient API to stream from a MetadataReader to a MetadataBuilder with modifications runtime#30443 lands and we're able to use it

2. @vargaz does something creative with the ILStrip tool emitting a remapping table and the runtime uses it to remap

3. We do nothing until an adequate API lands

[lewing]

cc @vitek-karas

[akoeplinger]

Another (cheap) option that we discussed is using the functionality @fanyang-mono introduced in IlStrip which zeroes out method bodies for all methods instead of a subset, this feature only relies on SRM. It'd make the binary size on disk larger but the compressed size probably stays similar.