Fix MSB3539 by moving "BaseIntermediateOutputPath" to "Directory.Build.props" (#220)

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: Atif Aziz <code@raboof.com>

Author: Copilot

Directory.Build.props

@@ -1,5 +1,12 @@
 <Project>
 
+  <!-- Roslyn 4.4 variant output paths must be set here (before Microsoft.Common.props)
+       to avoid MSB3539 warning. See: https://go.microsoft.com/fwlink/?linkid=869650 -->
+  <PropertyGroup Condition="'$(RoslynVersion)' == '4.4'">
+    <BaseOutputPath>$(MSBuildProjectDirectory)/bin/roslyn4.4/</BaseOutputPath>
+    <BaseIntermediateOutputPath>$(MSBuildProjectDirectory)/obj/roslyn4.4/</BaseIntermediateOutputPath>
+  </PropertyGroup>
+
   <PropertyGroup>
     <LangVersion>14</LangVersion>
     <Nullable>enable</Nullable>

src/DocoptNet/DocoptNet.csproj

@@ -5,8 +5,6 @@
   </PropertyGroup>
 
   <PropertyGroup Condition="'$(RoslynVersion)' == '4.4'">
-    <BaseOutputPath>$(_Roslyn44AnalyzerDir)</BaseOutputPath>
-    <BaseIntermediateOutputPath>$(MSBuildProjectDirectory)/obj/roslyn4.4/</BaseIntermediateOutputPath>
     <DefaultItemExcludes>$(DefaultItemExcludes);$(MSBuildProjectDirectory)/obj/**</DefaultItemExcludes>
     <DefineConstants>$(DefineConstants);ROSLYN4_4</DefineConstants>
   </PropertyGroup>