Hook after Clean

I use BUILD_DIR to compile boot2_stage boot loader of Raspberry Pi Pico but Clean clear only board folder...

I didn't find a solution for hook Clean (after) and I can offer you a small patch:

PlatformBase / base.py

    def on_clean(self, dir):            # <---
        pass

builder / tools / piotarget.py

    print("Done cleaning")
    return build_dir                    # <---

builder / main.py

if env.GetOption("clean") or is_clean_all:
    dir = env.PioClean(is_clean_all)    # <---
    env.PioPlatform().on_clean(dir)     # <---
    env.Exit(0)

platform.py

class MyPlatform(PlatformBase):
    def on_clean(self, dir):
        print('ON_CLEAN', dir) 
# RESULT: 
#   ON_CLEAN .....\.pio\build\test-board