CPS: Fix exporting definitions in CMake 4.1

Backport commit 37b15eda3b (CPS: Fix exporting definitions, 2025-11-21)
to CMake 4.1.

Export compile definitions to CPS using the correct attribute name.

Fixes: #27403

Source/cmExportPackageInfoGenerator.cxx

@@ -451,7 +451,7 @@ void cmExportPackageInfoGenerator::GenerateInterfaceCompileDefines(
   }
 
   if (!defines.empty()) {
-    component["compile_definitions"]["*"] = std::move(defines);
+    component["definitions"]["*"] = std::move(defines);
   }
 }