Set _buildConfiguration based on build mode

Use preprocessor directives to assign "Debug" or "Release" to _buildConfiguration depending on the build mode, ensuring correct configuration is used during test setup.

Author: Bertk

test/coverlet.MTP.validation.tests/CollectCoverageTests.cs

@@ -27,7 +27,11 @@ public class CollectCoverageTests
 
   public CollectCoverageTests()
   {
+#if DEBUG
     _buildConfiguration = "Debug";
+#else
+    _buildConfiguration = "Release";
+#endif
 
     // Get local packages path (adjust based on your build output)
     _repoRoot = Path.GetFullPath(Path.Combine(Directory.GetCurrentDirectory(), "..", "..", "..", ".."));