If wendline.core is built under buildout and setuptools exists only in
buildout environment, 'python setup.py' called inside make will fail
without this change.

Building 'wendelin.core'
Running easy_install:
"/path/to/python2.7" "-c" "import sys; sys.path[0:0] = ['/path/to/setuptools-19.6.2-py2.7.egg']; from setuptools.command.easy_install import main; main()"...
path_list=['/path/to/setuptools-19.6.2-py2.7.egg']
...
<<< setup.py: os.system('make %s PYTHON="%s"' % (target, sys.executable))
...
make[1]: Leaving directory '/tmp/xxx/wendelin.core-0.6/3rdparty/ccan'
/path/to/python2.7 setup.py ll_build_ext --inplace
Traceback (most recent call last):
  File "setup.py", line 18, in <module>
    from setuptools import setup, Extension, Command, find_packages
ImportError: No module named setuptools
Makefile:40: recipe for target 'bigfile/_bigfile.so' failed
make: *** [bigfile/_bigfile.so] Error 1
error: Setup script exited with error: Failed to execute `make all`