chore(CMake): make Lts top-level resilient to partial checkouts and optional RTI/doxygen\n\n- Guard ADD_DOXYGEN_TARGET with existence check

- Add only existing Lts subdirectories to allow partial migrations
- Make RTI optional in Lts/Common/CodeGen and guard RTI target properties
\nCo-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Lts/Common/CodeGen/CMakeLists.txt

@@ -4,7 +4,7 @@
 # $Author$
 #
 
-FIND_PACKAGE(RTI REQUIRED)
+FIND_PACKAGE(RTI)
 FIND_PACKAGE(Grantlee5 REQUIRED)
 
 NGL_ADD_LIBRARY(ALL codegen_base SHARED
@@ -27,12 +27,20 @@ NGL_TARGET_LINK_LIBRARIES(codegen_base
 NGL_TARGET_INCLUDE_DIRECTORIES(codegen_base
   PUBLIC
     ${CMAKE_CURRENT_SOURCE_DIR}/../
-    $<TARGET_PROPERTY:RTI::nddscpp2,INTERFACE_INCLUDE_DIRECTORIES>
-)
-NGL_TARGET_COMPILE_DEFINITIONS(codegen_base
-  PUBLIC
-    $<TARGET_PROPERTY:RTI::nddscpp2,INTERFACE_COMPILE_DEFINITIONS>
 )
+# If RTI target is available, propagate its include dirs/compile defs
+if (TARGET RTI::nddscpp2)
+  NGL_TARGET_INCLUDE_DIRECTORIES(codegen_base
+    PUBLIC
+      $<TARGET_PROPERTY:RTI::nddscpp2,INTERFACE_INCLUDE_DIRECTORIES>
+  )
+  NGL_TARGET_COMPILE_DEFINITIONS(codegen_base
+    PUBLIC
+      $<TARGET_PROPERTY:RTI::nddscpp2,INTERFACE_COMPILE_DEFINITIONS>
+  )
+else()
+  message(STATUS "RTI not found; building codegen_base without RTI include/compile definitions")
+endif()
 NGL_INSTALL_TARGET(codegen_base)
 
 NGL_ADD_LIBRARY(ALL codegen_grantlee STATIC