don't use docfx on non-windows platforms

Author: jaredcnance

src/JsonApiDotNetCore/JsonApiDotNetCore.csproj

@@ -13,11 +13,16 @@
     <RepositoryType>git</RepositoryType>
     <RepositoryUrl>https://github.com/json-api-dotnet/JsonApiDotNetCore</RepositoryUrl>
   </PropertyGroup>
+  <PropertyGroup>
+    <IsWindows Condition="'$(OS)' == 'Windows_NT'">true</IsWindows>
+  </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(TargetFramework)|$(Platform)'=='Release|netstandard2.0|AnyCPU'">
     <DocumentationFile>bin\Release\netstandard2.0\JsonApiDotNetCore.xml</DocumentationFile>
   </PropertyGroup>
-  <ItemGroup>
+  <ItemGroup Condition="$(IsWindows)">
     <PackageReference Include="docfx.console" Version="2.33.0" />
+  </ItemGroup>
+  <ItemGroup>
     <PackageReference Include="Microsoft.AspNetCore.Routing" Version="$(AspNetCoreVersion)" />
     <PackageReference Include="Microsoft.AspNetCore.Mvc" Version="$(AspNetCoreVersion)" />
     <PackageReference Include="Microsoft.EntityFrameworkCore" Version="$(EFCoreVersion)" />