This change moves powershell to .NET Core 2.0. Major changes are:
1. PowerShell assemblies are now targeting `netcoreapp2.0`. We are using `microsoft.netcore.app-2.0.0-preview1-001913-00`, which is from dotnet-core build 4/4/17. We cannot target `netstandard2.0` because the packages `System.Reflection.Emit` and `System.Reflection.Emit.Lightweight`, which are needed for powershell class, cannot be referenced when targeting `netstandard2.0`.
2. Refactor code to remove most CLR stub types and extension types.
3. Update build scripts to enable CI builds. The `-cache` section is specified to depend on `appveyor.yml`, so the cache will be invalidated if `appveyor.yml` is changed.
4. Ship `netcoreapp` reference assemblies with powershell to fix the issues in `Add-Type` (#2764). By default `Add-Type` will reference all those reference assemblies when compiling C# code. If `-ReferenceAssembly` is specified, then we search reference assemblies first, then the framework runtime assemblies, and lastly the loaded assemblies (possibly a third-party one that was already loaded).
5. `dotnet publish` generates executable on Unix platforms, but doesn't set "x" permission and thus it cannot execute. Currently, the "x" permission is set in the build script, `dotnet/cli` issue [#6286](https://github.com/dotnet/cli/issues/6286) is tracking this.
6. Replace the use of some APIs with the ones that take `SecureString`.
7. osx.10.12 is required to update to `netcoreapp2.0` because `dotnet-cli` 2.0.0-preview only works on osx.10.12.
8. Add dependency to `System.ValueTuple` to work around a ambiguous type identity issue in coreclr. The issue is tracked by `dotnet/corefx` [#17797](https://github.com/dotnet/corefx/issues/17797). When moving to newer version of `netcoreapp2.0`, we need to verify if this dependency is still needed.
Since the Travis CI OS X infrastructure is incredibly unstable,
we need to let the builds run on a best effort basis,
but not report failure and not hang a result until its finished.
With this setup, the Linux build dictates the success,
completely ignoring OS X.
GitHub's API is throttled to 60 requests per hour per IP address when
for non-authenticated calls, which was causing severe CI flakiness.
While this adds another set of URLs to update for each release, the
alternative was adding an OAuth token and maintaining its ownership.
Moreover, this code is simpler than the previous API parsing.
The previous failure we saw was because the most recent annotated tag
did not exist in the previous 50 commits. In my experience we've gone
about ~300 commits between tags, so I believe 1000 to be safe, but know
100 will not be.
Since we don't want to build packages for pull requests (as they cannot
get archived as artifacts), we need a slightly different build command,
and moving it to a script was cleaner.
This should enable building via PR from forks.
This token has read-only access to download the installer packages, but
should nonetheless be revoked and replaced with a wget download when the
repository goes public.
Unfortunately, Travis CI's OS X machines are 10.9.5, per
https://docs.travis-ci.com/user/osx-ci-environment/#CI-environment-OS.
While NuGet supports the RID, .NET Core does not yet publish 10.9
packages, resulting in a build failure we can't do anything about.
I've asked for best-effort support by providing runtime packages for
10.9 in dotnet/corefx#7731.
Revert "Add OS X 10.9 runtime"
This reverts commit 19ab0de84c.
