host python/python3: conditionally disable unicodedata

The host python always had --disable-unicodedata, regardless of the
corresponding configuration option BR2_PACKAGE_PYTHON_UNICODEDATA.
Since the host python is used to byte-compile python modules, this meant
that such modules could not contain unicode strings. For example, following
statement in a python module:
    print u"\N{SOLIDUS}"

would cause the byte-compilation to fail with message:
    SyntaxError: ("(unicode error) \\N escapes not supported (can't load
    unicodedata module)",

Instead, conditionally disable unicodedata based on
BR2_PACKAGE_PYTHON_UNICODEDATA, also for the host python.

This fixes bug #6542 (https://bugs.busybox.net/show_bug.cgi?id=6542

)

Reported-by: Gernot Vormayr <gvormayr@gmail.com>
Signed-off-by: Thomas De Schampheleire <thomas.de.schampheleire@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>