[mlir][python][NFC] Clean up nanobind compile options (#206559)

Follow-up to #204230.

Refactor nanobind warning suppression flags into `build_nanobind_lib`.
Drop duplicate RTTI and exception flags.

mlir/cmake/modules/AddMLIRPython.cmake

@@ -329,6 +329,16 @@ function(_mlir_python_install_sources name source_root_dir destination)
   )
 endfunction()
 
+# Define exception handling and RTTI flags.
+macro(_mlir_python_eh_rtti_flags)
+  set(eh_rtti_enable)
+  if(MSVC)
+    set(eh_rtti_enable /EHsc /GR)
+  elseif(LLVM_COMPILER_IS_GCC_COMPATIBLE OR CLANG_CL)
+    set(eh_rtti_enable -frtti -fexceptions)
+  endif()
+endmacro()
+
 function(build_nanobind_lib)
   cmake_parse_arguments(ARG
     ""
@@ -360,6 +370,27 @@ function(build_nanobind_lib)
     PRIVATE
     NB_DOMAIN=${ARG_MLIR_BINDINGS_PYTHON_NB_DOMAIN}
   )
+
+  if(NOT MLIR_DISABLE_CONFIGURE_PYTHON_DEV_PACKAGES
+     AND (LLVM_COMPILER_IS_GCC_COMPATIBLE OR CLANG_CL))
+    # Avoid some warnings from upstream nanobind.
+    # If a superproject set MLIR_DISABLE_CONFIGURE_PYTHON_DEV_PACKAGES, let
+    # the super project handle compile options as it wishes.
+    _mlir_python_eh_rtti_flags()
+    target_compile_options(${NB_LIBRARY_TARGET_NAME}
+      PRIVATE
+        -Wno-c++98-compat-extra-semi
+        -Wno-cast-qual
+        -Wno-covered-switch-default
+        -Wno-deprecated-literal-operator
+        -Wno-nested-anon-types
+        -Wno-unused-parameter
+        -Wno-zero-length-array
+        -Wno-missing-field-initializers
+        ${eh_rtti_enable})
+  endif()
+
+  # Apply caller-provided extra options last so they have higher precedence.
   target_compile_options(${NB_LIBRARY_TARGET_NAME}
     PRIVATE
       ${ARG_EXTRA_COMPILE_OPTIONS}
@@ -960,12 +991,7 @@ function(add_mlir_python_extension libname extname nb_library_target_name)
 
   # The extension itself must be compiled with RTTI and exceptions enabled.
   # Also, some warning classes triggered by nanobind are disabled.
-  set(eh_rtti_enable)
-  if (MSVC)
-    set(eh_rtti_enable /EHsc /GR)
-  elseif(LLVM_COMPILER_IS_GCC_COMPATIBLE OR CLANG_CL)
-    set(eh_rtti_enable -frtti -fexceptions)
-  endif ()
+  _mlir_python_eh_rtti_flags()
 
   if(ARG__PRIVATE_SUPPORT_LIB)
     add_library(${libname} SHARED ${ARG_SOURCES})
@@ -1021,18 +1047,6 @@ function(add_mlir_python_extension libname extname nb_library_target_name)
     # Avoid some warnings from upstream nanobind.
     # If a superproject set MLIR_DISABLE_CONFIGURE_PYTHON_DEV_PACKAGES, let
     # the super project handle compile options as it wishes.
-    target_compile_options(${nb_library_target_name}
-      PRIVATE
-        -Wno-c++98-compat-extra-semi
-        -Wno-cast-qual
-        -Wno-covered-switch-default
-        -Wno-deprecated-literal-operator
-        -Wno-nested-anon-types
-        -Wno-unused-parameter
-        -Wno-zero-length-array
-        -Wno-missing-field-initializers
-        ${eh_rtti_enable})
-
     target_compile_options(${libname}
       PRIVATE
         -Wno-c++98-compat-extra-semi
@@ -1042,8 +1056,7 @@ function(add_mlir_python_extension libname extname nb_library_target_name)
         -Wno-nested-anon-types
         -Wno-unused-parameter
         -Wno-zero-length-array
-        -Wno-missing-field-initializers
-        ${eh_rtti_enable})
+        -Wno-missing-field-initializers)
   endif()
 
   if(APPLE)