Today we download crossgen for all supported runtime ids. This
introduces a dependency on having builds for all supported platforms
in order to build the CLI on a single platform. This is problematic
for the build from source effort because we only build artifacts for a
specific rid (the RID of the host/target).
Update the CrossGen.Dependencies project to restore for only the RID
we are building for.
* Add support to build with the linux portable
* Pass targets to run for the linux portable
* Address PR comments
* Update the bootstrapper version
* Address the PR comments for improving the help text
* Fixing permissions
Use the crossgen and jit that comes with Microsoft.NETCore.App so we don't have to keep a corresponding CoreCLR version around.
Remove workarounds for crossgen bug https://github.com/dotnet/coreclr/issues/9118
