Use MSBuild version comparison functions instead of numerical comparisons (#2843)

Replace direct numerical comparisons with MSBuild's built-in version comparison functions for better reliability and correctness.

Changes:
- Updated Directory.Build.targets to use MSBuild::VersionGreaterThanOrEquals for RoslynVersion comparisons
- Changed $(RoslynVersion) >= 4.7 to $([MSBuild]::VersionGreaterThanOrEquals('$(RoslynVersion)', '4.7'))
- Changed $(RoslynVersion) >= 4.14 to $([MSBuild]::VersionGreaterThanOrEquals('$(RoslynVersion)', '4.14'))

Benefits:
- Correct semantic version comparison (handles "4.10" > "4.9" properly)
- Better compatibility across different MSBuild versions
- Type-safe version comparisons

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-authored-by: Claude <noreply@anthropic.com>

Author: thomhurst

Directory.Build.targets

@@ -1,6 +1,6 @@
 <Project>
   <PropertyGroup>
-    <DefineConstants Condition="$(RoslynVersion) >= 4.7">$(DefineConstants);ROSLYN4_7_OR_GREATER</DefineConstants>
-    <DefineConstants Condition="$(RoslynVersion) >= 4.14">$(DefineConstants);ROSLYN4_14_OR_GREATER</DefineConstants>
+    <DefineConstants Condition="$([MSBuild]::VersionGreaterThanOrEquals('$(RoslynVersion)', '4.7'))">$(DefineConstants);ROSLYN4_7_OR_GREATER</DefineConstants>
+    <DefineConstants Condition="$([MSBuild]::VersionGreaterThanOrEquals('$(RoslynVersion)', '4.14'))">$(DefineConstants);ROSLYN4_14_OR_GREATER</DefineConstants>
   </PropertyGroup>
 </Project>