[scons] code cleanup for scons script. (#10429)

* [scons] move project_generation to targets; code clean for building.py.

tools/preprocessor.py

@@ -0,0 +1,89 @@
+# -*- coding: utf-8 -*-
+#
+# File      : preprocessor.py
+# This file is part of RT-Thread RTOS
+# COPYRIGHT (C) 2006 - 2025, RT-Thread Development Team
+#
+#  This program is free software; you can redistribute it and/or modify
+#  it under the terms of the GNU General Public License as published by
+#  the Free Software Foundation; either version 2 of the License, or
+#  (at your option) any later version.
+#
+#  This program is distributed in the hope that it will be useful,
+#  but WITHOUT ANY WARRANTY; without even the implied warranty of
+#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#  GNU General Public License for more details.
+#
+#  You should have received a copy of the GNU General Public License along
+#  with this program; if not, write to the Free Software Foundation, Inc.,
+#  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+#
+# Change Logs:
+# Date           Author       Notes
+# 2025-01-05     Assistant    Extract SCons PreProcessor patch to independent class
+
+from SCons.Script import *
+
+class SConsPreProcessorPatch:
+    """
+    SCons PreProcessor patch class
+    
+    This class provides methods to patch the SCons PreProcessor
+    to handle conditional compilation directives properly.
+    """
+    
+    def __init__(self):
+        """Initialize the PreProcessor patch"""
+        self._patched_preprocessor = None
+        self._apply_patch()
+    
+    def _apply_patch(self):
+        """
+        Apply the patch to SCons PreProcessor
+        
+        This method patches the SCons.cpp.PreProcessor class with
+        custom methods for handling includes during conditional compilation.
+        """
+        from SCons import cpp
+        
+        # Store reference to original PreProcessor
+        self._patched_preprocessor = cpp.PreProcessor
+        
+        # Create bound methods for the patch
+        def start_handling_includes(preprocessor_self, t=None):
+            d = preprocessor_self.dispatch_table
+            p = preprocessor_self.stack[-1] if preprocessor_self.stack else preprocessor_self.default_table
+            for k in ('import', 'include', 'include_next', 'define'):
+                d[k] = p[k]
+        
+        def stop_handling_includes(preprocessor_self, t=None):
+            d = preprocessor_self.dispatch_table
+            d['import'] = preprocessor_self.do_nothing
+            d['include'] = preprocessor_self.do_nothing
+            d['include_next'] = preprocessor_self.do_nothing
+            d['define'] = preprocessor_self.do_nothing
+        
+        # Apply the patch methods
+        self._patched_preprocessor.start_handling_includes = start_handling_includes
+        self._patched_preprocessor.stop_handling_includes = stop_handling_includes
+    
+    def get_patched_preprocessor(self):
+        return self._patched_preprocessor
+    
+    def create_preprocessor_instance(self):
+        return self._patched_preprocessor()
+
+# Global instance for easy access
+_preprocessor_patch = None
+
+def get_patched_preprocessor():
+    global _preprocessor_patch
+    if _preprocessor_patch is None:
+        _preprocessor_patch = SConsPreProcessorPatch()
+    return _preprocessor_patch.get_patched_preprocessor()
+
+def create_preprocessor_instance():
+    global _preprocessor_patch
+    if _preprocessor_patch is None:
+        _preprocessor_patch = SConsPreProcessorPatch()
+    return _preprocessor_patch.create_preprocessor_instance()