Allow reflecting on DebuggableAttribute on CoreRT

[MichalStrehovsky]

See dotnet/corert#6955 (comment).

BenchmakeDotNet reflects on this attribute here:

BenchmarkDotNet/src/BenchmarkDotNet/Extensions/AssemblyExtensions.cs

Lines 28 to 38 in a76f438

	private static bool? Read(DebuggableAttribute debuggableAttribute, string propertyName)
	{
	// the properties are implemented (https://github.com/dotnet/coreclr/pull/6153)
	// but not exposed in corefx Contracts due to .NET Standard versioning problems (https://github.com/dotnet/corefx/issues/13717)
	// so we need to use reflection to read this simple property...
	var propertyInfo = typeof(DebuggableAttribute).GetProperty(propertyName);
	if (debuggableAttribute == null || propertyInfo == null)
	return null;
	return (bool)propertyInfo.GetValue(debuggableAttribute);
	}

[jkotas]

Benchmark.NET is targeting .NET Standard 2.0: https://github.com/dotnet/BenchmarkDotNet/blob/master/src/BenchmarkDotNet/BenchmarkDotNet.csproj#L5. These methods are available in .NET Standard 2.0.

Would it be better to just avoid the reflection altogether?

[adamsitnik]

@MichalStrehovsky big thanks for the PR! I am glad I am not the only user of our CoreRtToolchain anymore!

@jkotas you are right, the comments in the code are from the dnx or netcoreapp1.0 era ;)

[adamsitnik]

I am going to merge this now and fix the way we use this attribute.

I am going to also add one more integration test to make sure we support the latest version of CoreRT.

So far our tests were running against const version of CoreRT:

BenchmarkDotNet/tests/BenchmarkDotNet.IntegrationTests/CoreRtTests.cs

Line 27 in 6fb8309

.UseCoreRtNuGet(microsoftDotNetILCompilerVersion: "1.0.0-alpha-26414-01") // we test against specific version to keep this test stable

[MichalStrehovsky]

I am glad I am not the only user of our CoreRtToolchain anymore!

You should add telemetry. I'm sure there's many of us :).