chore(cmake): carry option-driven defines on pybind11_headers INTERFACE

PYBIND11_DISABLE_HANDLE_TYPE_NAME_DEFAULT_IMPLEMENTATION and
PYBIND11_SIMPLE_GIL_MANAGEMENT were directory-scoped
add_compile_definitions, which only reached the master-project test
build. On the pybind11_headers INTERFACE (like
PYBIND11_INTERNALS_VERSION) they also apply in add_subdirectory mode
and in the exported/installed targets.

Assisted-by: ClaudeCode:claude-fable-5

Author: henryiii

CMakeLists.txt

@@ -109,13 +109,6 @@ if(NOT DEFINED PYBIND11_USE_CROSSCOMPILING)
 endif()
 option(PYBIND11_USE_CROSSCOMPILING "Respect CMAKE_CROSSCOMPILING" OFF)
 
-if(PYBIND11_DISABLE_HANDLE_TYPE_NAME_DEFAULT_IMPLEMENTATION)
-  add_compile_definitions(PYBIND11_DISABLE_HANDLE_TYPE_NAME_DEFAULT_IMPLEMENTATION)
-endif()
-if(PYBIND11_SIMPLE_GIL_MANAGEMENT)
-  add_compile_definitions(PYBIND11_SIMPLE_GIL_MANAGEMENT)
-endif()
-
 cmake_dependent_option(
   USE_PYTHON_INCLUDE_DIR
   "Install pybind11 headers in Python include directory instead of default installation prefix"
@@ -307,6 +300,13 @@ if(NOT TARGET pybind11_headers)
     target_compile_definitions(
       pybind11_headers INTERFACE "PYBIND11_INTERNALS_VERSION=${PYBIND11_INTERNALS_VERSION}")
   endif()
+  if(PYBIND11_DISABLE_HANDLE_TYPE_NAME_DEFAULT_IMPLEMENTATION)
+    target_compile_definitions(pybind11_headers
+                               INTERFACE PYBIND11_DISABLE_HANDLE_TYPE_NAME_DEFAULT_IMPLEMENTATION)
+  endif()
+  if(PYBIND11_SIMPLE_GIL_MANAGEMENT)
+    target_compile_definitions(pybind11_headers INTERFACE PYBIND11_SIMPLE_GIL_MANAGEMENT)
+  endif()
 else()
   # It is invalid to install a target twice, too.
   set(PYBIND11_INSTALL OFF)