AttributeError: 'tuple' object has no attribute 'lower'

[ljsenjj]

在AWStudio中载了HelloDesigner-Demo示例项目，执行scons LINUX_FB=true BUILD_DIR=arm时报错：

{'LINUX_FB': 'true', 'BUILD_DIR': 'arm'}
AttributeError: 'tuple' object has no attribute 'lower':
File "F:\Project\AWStudio\Workspace\HelloDesigner-Demo\SConstruct", line 12:
helper.call(DefaultEnvironment)
File "D:\dev_idea\AWStudio\AWTK\SDK\awtk-linux-fb../awtk/scripts\app_helper_base.py", line 599:
env = DefaultEnvironment(
File "D:\dev_env\Python\Python38\lib\site-packages\scons-4.3.0-py3.8.egg\SCons\Defaults.py", line 83:
default_env = SCons.Environment.Environment(*args, **kw)
File "D:\dev_env\Python\Python38\lib\site-packages\scons-4.3.0-py3.8.egg\SCons\Environment.py", line 1010:
apply_tools(self, tools, toolpath)
File "D:\dev_env\Python\Python38\lib\site-packages\scons-4.3.0-py3.8.egg\SCons\Environment.py", line 116:
_ = env.Tool(tool)
File "D:\dev_env\Python\Python38\lib\site-packages\scons-4.3.0-py3.8.egg\SCons\Environment.py", line 1879:
tool(self)
File "D:\dev_env\Python\Python38\lib\site-packages\scons-4.3.0-py3.8.egg\SCons\Tool_init.py", line 273:
self.generate(env, *args, **kw)
File "D:\dev_env\Python\Python38\lib\site-packages\scons-4.3.0-py3.8.egg\SCons\Tool\default.py", line 40:
for t in SCons.Tool.tool_list(env['PLATFORM'], env):
File "D:\dev_env\Python\Python38\lib\site-packages\scons-4.3.0-py3.8.egg\SCons\Tool_init_.py", line 775:
c_compiler = FindTool(c_compilers, env) or c_compilers[0]
File "D:\dev_env\Python\Python38\lib\site-packages\scons-4.3.0-py3.8.egg\SCons\Tool_init_.py", line 678:
if t.exists(env):
File "D:\dev_env\Python\Python38\lib\site-packages\scons-4.3.0-py3.8.egg\SCons\Tool\msvc.py", line 319:
return msvc_exists(env)
File "D:\dev_env\Python\Python38\lib\site-packages\scons-4.3.0-py3.8.egg\SCons\Tool\MSCommon\vc.py", line 970:
vcs = get_installed_vcs(env)
File "D:\dev_env\Python\Python38\lib\site-packages\scons-4.3.0-py3.8.egg\SCons\Tool\MSCommon\vc.py", line 695:
if _check_cl_exists_in_vc_dir(env, VC_DIR, ver):
File "D:\dev_env\Python\Python38\lib\site-packages\scons-4.3.0-py3.8.egg\SCons\Tool\MSCommon\vc.py", line 574:
(host_platform, target_platform, req_target_platform) = get_host_target(env)
File "D:\dev_env\Python\Python38\lib\site-packages\scons-4.3.0-py3.8.egg\SCons\Tool\MSCommon\vc.py", line 221:
target = _ARCH_TO_CANONICAL[target_platform.lower()]

不加“LINUX_FB=true BUILD_DIR=arm”时可正常编译，这是啥原因？