Updated NuGet.exe

aspnet/lib/.nuget/NuGet.targets

@@ -45,7 +45,7 @@
         <PackageSources Condition=" $(PackageSources) == '' ">@(PackageSource)</PackageSources>
         
         <NuGetCommand Condition=" '$(OS)' == 'Windows_NT'">"$(NuGetExePath)"</NuGetCommand>
-        <NuGetCommand Condition=" '$(OS)' != 'Windows_NT' ">mono --runtime=v4.0.30319 $(NuGetExePath)</NuGetCommand>
+        <NuGetCommand Condition=" '$(OS)' != 'Windows_NT' ">mono $(NuGetExePath)</NuGetCommand>
 
         <PackageOutputDir Condition="$(PackageOutputDir) == ''">$(TargetDir.Trim('\\'))</PackageOutputDir>
         
@@ -132,4 +132,4 @@
             </Code>
         </Task>
     </UsingTask>
-</Project>
+</Project>