chore(cmake): make RTI codegen macro tolerant when RTI is not installed (skip RTIDDSGEN)

cmake/MacroRTIDDSGen.cmake

@@ -14,7 +14,12 @@
 
 
 MACRO(RTIDDSGEN srcList infile)
-  FIND_PACKAGE(RTI REQUIRED)
+  # RTI (DDS) code generation is optional during migration; if RTI is not found, skip code generation.
+  FIND_PACKAGE(RTI)
+  if (NOT RTI_FOUND)
+    message(STATUS "RTI not found; skipping RTI IDL code generation for ${infile}")
+    return()
+  endif()
 
   SET(input ${infile})
   IF(NOT IS_ABSOLUTE ${input})