distutils/steuptools: Fix files layout and unbreak builds

The last two distutils changes progressivly broke the builds. Firstly they
moved things from the site_packages directory to being higher up the tree
which introduced package QA warnings as a side effect. Secondly, it interacts
badly with setuptools which passes in --root=${D} itself.

This patch restores the original directory layout, hence fixing the QA
warnings and also passes extra options to setuptools to deal with the
--root option it passes.

(From OE-Core rev: bed18d5df7915e4127a538be9c7550e185c8c850)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/setuptools.bbclass

@@ -5,4 +5,5 @@ DEPENDS += "python-setuptools-native"
 DISTUTILS_INSTALL_ARGS = "--root=${D} \
     --single-version-externally-managed \
     --prefix=${prefix} \
+    --install-lib=${PYTHON_SITEPACKAGES_DIR} \
     --install-data=${datadir}"