Fix MonoEnableLLVM* properties (dotnet#111746)

Counter-part change in dotnet/sdk#46239

Author: ViktorHofer

eng/DotNetBuild.props

@@ -37,7 +37,7 @@
     <!-- NativeAOT builds are short -->
     <ShortStack Condition="'$(DotNetBuildRuntimeNativeAOTRuntimePack)' == 'true'">true</ShortStack>
     <!-- Mono LLVM builds are short -->
-    <ShortStack Condition="'$(MonoEnableLLVM)' == 'true' or '$(MonoAOTEnableLLVM)' == 'true'">true</ShortStack>
+    <ShortStack Condition="'$(DotNetBuildMonoEnableLLVM)' == 'true' or '$(DotNetBuildMonoAOTEnableLLVM)' == 'true'">true</ShortStack>
     <!-- Mono AOT cross compiler builds are short -->
     <ShortStack Condition="'$(DotNetBuildMonoCrossAOT)' == 'true'">true</ShortStack>
   </PropertyGroup>