fixes argument list too long error when building.

Author: kdschlosser

builder/esp32.py

@@ -1231,6 +1231,18 @@ def update_mpconfigport():
     write_file(MPCONFIGPORT_PATH, data)
 
 
+def update_mkrules():
+    mkrules_path = 'lib/micropython/py/mkrules.cmake'
+    with open(mkrules_path, 'rb') as f:
+        data = f.read().decode('utf-8')
+
+    if 'REMOVE_DUPLICATES' not in data:
+        data = data.replace('add_custom_command(', 'list(REMOVE_DUPLICATES MICROPY_CPP_FLAGS)\n\nadd_custom_command(', 1)
+
+        with open(mkrules_path, 'wb') as f:
+            f.write(data.encode('utf-8'))
+
+
 def update_main():
     # data = read_file('esp32', MAIN_PATH)
 
@@ -1429,6 +1441,7 @@ def compile(*args):  # NOQA
     update_panic_handler()
     update_mpconfigboard()
     update_mpconfigport()
+    update_mkrules()
 
     copy_micropy_updates('esp32')