cmGlobalGenerator: Only compute build files for all targets

If we're creating generation objects for imported targets only, we
don't need the export sets. Only compute build file generators
if generating for all targets.

Fixes: #23709

Source/cmGlobalGenerator.cxx

@@ -1361,7 +1361,9 @@ void cmGlobalGenerator::CreateGenerationObjects(TargetTypes targetTypes)
     this->CheckTargetProperties();
   }
   this->CreateGeneratorTargets(targetTypes);
-  this->ComputeBuildFileGenerators();
+  if (targetTypes == TargetTypes::AllTargets) {
+    this->ComputeBuildFileGenerators();
+  }
 }
 
 void cmGlobalGenerator::CreateImportedGenerationObjects(

Tests/RunCMake/export/RunCMakeTest.cmake

@@ -18,3 +18,4 @@ run_cmake(DependOnDoubleExport)
 run_cmake(UnknownExport)
 run_cmake(NamelinkOnlyExport)
 run_cmake(SeparateNamelinkExport)
+run_cmake(TryCompileExport)

Tests/RunCMake/export/TryCompileExport.cmake

@@ -0,0 +1,9 @@
+enable_language(CXX)
+
+add_library(interface INTERFACE)
+install(TARGETS interface EXPORT export)
+export(EXPORT export)
+
+add_library(imported IMPORTED INTERFACE)
+
+try_compile(tc "${CMAKE_CURRENT_BINARY_DIR}/tc" "${CMAKE_CURRENT_SOURCE_DIR}/empty.cpp" LINK_LIBRARIES imported)