Fix ikvm-build-2 for strong naming

[timmahon]

Updates

• ImportCspBlob caused an exception "KeySet not found" when trying to sign the hash. This update replaces the usage of ImportCspBlob and ExportCspBlob calls on the RSACryptoServiceProvider with importing and exporting RSAParameters instead.
• Helper functions to transform SNK byte array to RSAParameters, and also to ExportPublicKey byte array from RSAParameters.
• build.core.cmd now completes, and with the resulting binaries, I was able to cross-compile a java jar and sign it with a different snk key and run the resulting DLLs under .NET 6

Problems

• Has the following warning, but unsure if this is safe to ignore
  EXEC : warning : assembly "IKVM.OpenJDK.Core.dll" is ignored as previously loaded assembly "IKVM.OpenJDK.Core.dll" has the same identity "IKVM.OpenJDK.Core, Version=8.5.0.3, Culture=neutral, PublicKeyToken=13235d27fcbfff58" [\ikvm\openjdk\openjdk.csproj] EXEC : warning : Running ikvmstub on ikvmc compiled assemblies is not supported. [\ikvm\openjdk\openjdk.csproj]

[NightOwl888]

Thanks for the PR!

I gave it a try and can confirm your findings. I merge these branches back into master so contributors can consolidate their efforts there. And when I get a free moment, I will put together a build pipeline and the NuGet packaging (at least for .NET Core).

Do note that build.framework.cmd also isn't currently functioning, so any efforts we can put together to get that working would be appreciated.