src/poky:buildtools-tarball: Add python3-setuptools

After the dependency on setuptools was dropped from python3-testtools, this
exposed eSDK dependencies in devtool and recipetool on python3-setuptools. Add
this to buildtools to fix build failures after the testtools fixes.

(From OE-Core rev: c4431b4dd27d290024472f315858a63aea2a733c)

Signed-off-by: Richard Purdie <[email protected]>

Author: rpurdie