Update the License to MIT for coreclr repo (#11482)

Author: tarekgh

dir.props

@@ -138,6 +138,7 @@
 
   <!-- Packaging properties -->
   <PropertyGroup>
+    <LicenseUrl>https://github.com/dotnet/corefx/blob/master/LICENSE</LicenseUrl>
     <PreReleaseLabel>preview2</PreReleaseLabel>
     <PackageDescriptionFile>$(SourceDir).nuget/descriptions.json</PackageDescriptionFile>
     <PackageLicenseFile>$(SourceDir).nuget/dotnet_library_license.txt</PackageLicenseFile>

src/.nuget/dir.targets

@@ -84,5 +84,12 @@
     </ItemGroup>
   </Target>
 
+  <!-- OverrideLicenseUrl is temporary till we update the buildtools to v2 -->  
+  <Target Name="OverrideLicenseUrl" BeforeTargets="GenerateNuSpec">
+    <PropertyGroup>
+      <LicenseUrl>https://github.com/dotnet/corefx/blob/master/LICENSE</LicenseUrl>
+    </PropertyGroup>
+  </Target>
+
   <Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory)\.., dir.targets))\dir.targets" />
 </Project>