Add RuntimeIdentifer(s) properties to project constants

These are typically useful in addition to TFM.

Author: kzu

src/ThisAssembly.Project/ThisAssembly.Project.props

@@ -7,6 +7,9 @@
     <ProjectProperty Include="TargetFrameworkIdentifier" />
     <ProjectProperty Include="TargetFrameworkMoniker" />
     <ProjectProperty Include="TargetFrameworkVersion" />
+
+    <ProjectProperty Include="RuntimeIdentifier" />
+    <ProjectProperty Include="RuntimeIdentifiers" />
   </ItemGroup>
 
 </Project>

src/ThisAssembly.Tests/Tests.cs

@@ -124,6 +124,11 @@ public void CanUseHierarchicalMetadata()
     public void CanUseProjectProperty()
         => Assert.Equal("Bar", ThisAssembly.Project.Foo);
 
+    /// <summary />
+    [Fact]
+    public void CanUseProjectProperty2()
+        => Assert.NotEmpty(ThisAssembly.Project.RuntimeIdentifiers);
+
     /// <summary />
     [Fact]
     public void CanUseStringsNamedArguments()

src/ThisAssembly.Tests/ThisAssembly.Tests.csproj

@@ -26,6 +26,7 @@
     <ProjectFileComment>$(ProjectFile)</ProjectFileComment>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
     <WarningsAsErrors>true</WarningsAsErrors>
+    <RuntimeIdentifiers>win-x64;linux-x86</RuntimeIdentifiers>
   </PropertyGroup>
 
   <Import Project="..\*\ThisAssembly*.props" />