Use local-build corehost.exe
This is staying in the repo, so we can copy the local-built version.
Copy deps and deps.json, make sure corehost temp dir exists
Add additional runtimes to the sharedframework's project.json
Delete an unused file, modify crossgen target condition
* sharedhost\project.json is unused. It is copied from the local build.
* the crossgen target was conditioned on an environment variable, but the
variable could be set to anything. Instead, make sure it is either
"true" or "1".
Use stage2 instead of stage0 for shared framework restore
- Use Crossgen's Ready To Run mode on all of the managed assemblies
that make up the shared framework.
- Upgrade the version of the shared framework to match what is used
in the rest of CLI (see the comment in SharedFrameworkTargets.cs to
understand why this is needed).
- Remove the IL mscorlib.dll image, since the Crossgen'd image is
already published.
Fixesdotnet/corefx#6753
Ideally in the project.json for the shared host we would just list the
actual package that holds the shared host, instead of all of
NetStandard.Library, but doing some leads to compliation errors, since
publish wants to include a compile step that has a generated
AssemblyAttributes file which references types like System.String.
