quite a bit, too much to summarize here

packages/Microsoft.Bcl.Build.1.0.14/tools/Uninstall.ps1

@@ -0,0 +1,26 @@
+param($installPath, $toolsPath, $package, $project)
+ 
+  # Need to load MSBuild assembly if it's not loaded yet.
+  Add-Type -AssemblyName 'Microsoft.Build, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'
+
+  # Grab the loaded MSBuild project for the project
+  # Normalize project path before calling GetLoadedProjects as it performs a string based match
+  $msbuild = [Microsoft.Build.Evaluation.ProjectCollection]::GlobalProjectCollection.GetLoadedProjects([System.IO.Path]::GetFullPath($project.FullName)) | Select-Object -First 1
+
+  # Find all the imports and targets added by this package.
+  $itemsToRemove = @()
+
+  # Allow many in case a past package was incorrectly uninstalled
+  $itemsToRemove += $msbuild.Xml.Imports | Where-Object { $_.Project.EndsWith($package.Id + '.targets') }
+  $itemsToRemove += $msbuild.Xml.Targets | Where-Object { $_.Name -eq "EnsureBclBuildImported" }
+  
+  # Remove the elements and save the project
+  if ($itemsToRemove -and $itemsToRemove.length)
+  {
+     foreach ($itemToRemove in $itemsToRemove)
+     {
+         $msbuild.Xml.RemoveChild($itemToRemove) | out-null
+     }
+     
+     $project.Save()
+  }