set stride root folder next to entry point

[joreg]

[tebjan]

@azeno this is where the base folder gets initialized, should be easy to add an initial root folder parameter: https://github.com/stride3d/stride/blob/master/sources/core/Stride.Core/PlatformFolders.cs

[azeno]

You think? It's all static. We need it per entry point, when I see static it already sounds wrong to me. Or do you have something easy in mind I don't see?

[azeno]

See also https://github.com/vvvv/VL.StandardLibs/issues/492