Update the License Url for packages

Author: tarekgh

Packaging.props

@@ -22,6 +22,7 @@
     <!-- by default all packages will use the same version which revs with respect to product version -->
     <PackageVersion Condition="'$(PackageVersion)' == ''">4.4.0</PackageVersion>
     <SkipValidatePackageTargetFramework>true</SkipValidatePackageTargetFramework>
+    <LicenseUrl>https://github.com/dotnet/corefx/blob/master/LICENSE</LicenseUrl>    
   </PropertyGroup>
 
   <Import Condition="Exists('pkg/baseline/baseline.props') AND '$(MSBuildProjectExtension)' == '.pkgproj'" Project="pkg/baseline/baseline.props" />

dir.targets

@@ -107,6 +107,13 @@
     </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>  
+  
   <!-- This import is needed because we're still using project.json to restore packages. 
        Once we switch to MSBuild it will automatically handle target imports from the packages themselves. -->
   <Import Condition="'$(TargetGroup)'=='netstandard2.0' and Exists('$(PackagesDir)NETStandard.Library\2.0.0-$(StandardExpectedPrerelease)\build\netstandard2.0\NETStandard.Library.targets')"