[yocto] SOLUTION: Re: Updating daisy -> Python.h not found

[Tyler Hall]

That patch changed python3-config to use distutils.sysconfig to get
paths. That was already patched by OE to use environment variables to
substitute the correct path, but it seems there's nothing guaranteeing
those variables are exported.

> PREFIX = os.path.normpath(sys.prefix).replace( os.getenv("BUILD_SYS"),
> os.getenv("HOST_SYS") )
>
> This gives error
>
> TypeError: Can't convert 'NoneType' object to str implicitly

It may have worked previously because python3-config returned the path
to the native sysroot and it compiled successfully despite picking up
the header from the wrong place.

There are a few python recipes that export these variables explicitly,
but it doesn't seem like something that clients should have to know
about.

>From python-pycurl:
>
> # need to export these variables for python-config to work
> export BUILD_SYS
> export HOST_SYS
> export STAGING_INCDIR
> export STAGING_LIBDIR

This is also done in python-pygobject and python-dbus. Is this
something that distutils.bbclass should do?

-Tyler