[main] Update dependencies from mono/linker (#51308)

* Update dependencies from https://github.com/mono/linker build 20210415.1

Microsoft.NET.ILLink.Tasks
 From Version 6.0.100-preview.2.21212.5 -> To Version 6.0.100-preview.2.21215.1

* Update dependencies from https://github.com/mono/linker build 20210415.2

Microsoft.NET.ILLink.Tasks
 From Version 6.0.100-preview.2.21212.5 -> To Version 6.0.100-preview.2.21215.2
Co-authored-by: Ndotnet-maestro[bot] <dotnet-maestro[bot]@users.noreply.github.com>
Co-authored-by: NAlexander Köplinger <alex.koeplinger@outlook.com>

eng/Version.Details.xml

@@ -194,9 +194,9 @@
       <Uri>https://github.com/dotnet/runtime</Uri>
       <Sha>355eff52bed00e7ca9d4a6d769ddbe2bbadbea47</Sha>
     </Dependency>
-    <Dependency Name="Microsoft.NET.ILLink.Tasks" Version="6.0.100-preview.2.21212.5">
+    <Dependency Name="Microsoft.NET.ILLink.Tasks" Version="6.0.100-preview.2.21215.2">
       <Uri>https://github.com/mono/linker</Uri>
-      <Sha>7f7eb298a1ea6a144b2fb795ca10feb138e3988a</Sha>
+      <Sha>1ed6f39a6e716b42fa5e478dcfd30a59f1c8f25e</Sha>
     </Dependency>
     <Dependency Name="Microsoft.DotNet.XHarness.TestRunners.Xunit" Version="1.0.0-prerelease.21214.1">
       <Uri>https://github.com/dotnet/xharness</Uri>

eng/Versions.props

@@ -165,7 +165,7 @@
     <!-- Docs -->
     <MicrosoftPrivateIntellisenseVersion>5.0.0-preview-20201009.2</MicrosoftPrivateIntellisenseVersion>
     <!-- ILLink -->
-    <MicrosoftNETILLinkTasksVersion>6.0.100-preview.2.21212.5</MicrosoftNETILLinkTasksVersion>
+    <MicrosoftNETILLinkTasksVersion>6.0.100-preview.2.21215.2</MicrosoftNETILLinkTasksVersion>
     <!-- ICU -->
     <MicrosoftNETCoreRuntimeICUTransportVersion>6.0.0-preview.4.21212.2</MicrosoftNETCoreRuntimeICUTransportVersion>
     <!-- Mono LLVM -->