NCrunch does not work with MSBuild.Sdk.Extras based project.

MSBuild.Sdk.Extras can be found here: https://github.com/onovotny/MSBuildSdkExtras/blob/master/README.md

Here is the sample project (not mine): https://github.com/martinfletcher/xamarin-multitarget-sample/blob/master/MyCrossPlatformPlugin/MyCrossPlatformPlugin.csproj

I was trying to use Extras to multitarget `Xamarin.iOS` in DryIoc and got the error with NCrunch. MSBuild build worked fine.

Here is the DryIoc.csproj at that time (now reverted): https://github.com/dadhi/DryIoc/blob/e84619db5ed89b6cbbf269e98fdbd4e48b29d778/src/DryIoc/DryIoc.csproj

Hi, thanks for sharing this problem.

Please note that right now Xamarin is not a supported platform under NCrunch (for building or test environments). We have performed no testing or integration in this area - https://www.ncrunch.net/support/frameworks.

If you'd like to see support added, you're very welcome to vote for this to be added through uservoice.

Thank you @Remco.

I have re-checked that without Xamarin target, NCrunch understands Extras just fine.
This is enough for now, cause I can switch Off some frameworks in dev-mode (with NCrunch), and include everything back on CI (w/out NCrunch).

```
<Project Sdk="MSBuild.Sdk.Extras/1.6.61">

<PropertyGroup>
<TargetFrameworks Condition="'$(DevMode)' == 'true' ">netstandard2.0</TargetFrameworks>
<TargetFrameworks Condition="'$(DevMode)' != 'true' ">netstandard2.0;Xamarin.iOS10</TargetFrameworks>
</PropertyGroup>

<PropertyGroup Condition="'$(TargetFramework)' == 'Xamarin.iOS10'">
</PropertyGroup>

</Project>
```