🔨 Build scripts cleanup (#27157)

Co-authored-by: Scott Lahteine <thinkyhead@users.noreply.github.com>

buildroot/share/PlatformIO/scripts/common-dependencies-post.py

@@ -4,7 +4,9 @@
 #
 import pioutil
 if pioutil.is_pio_build():
-    Import("env", "projenv")
+    env = pioutil.env
+    projenv = env
+    Import("projenv") # src_dir environment. Only for post: scripts!
 
     def apply_board_build_flags():
         if not 'BOARD_CUSTOM_BUILD_FLAGS' in env['MARLIN_FEATURES']: