setuptools: move stuff to declarative cfg if possible [skip ci]

We're down to just declaring the data files in python now.

setup.cfg can, uniquely, retrieve version info by trying to parse the
AST for simple assignments (which we use) instead of importing the
entire module.

setup.cfg

@@ -1,4 +1,6 @@
 [metadata]
+name = meson
+version = attr: mesonbuild.coredata.version
 description = A high performance build system
 author = Jussi Pakkanen
 author_email = jpakkane@gmail.com
@@ -29,16 +31,24 @@ classifiers =
 long_description = Meson is a cross-platform build system designed to be both as fast and as user friendly as possible. It supports many languages and compilers, including GCC, Clang, PGI, Intel, and Visual Studio. Its build definitions are written in a simple non-Turing complete DSL.
 
 [options]
+packages = find:
 python_requires = >= 3.6
 setup_requires =
   setuptools
 
+[options.entry_points]
+console_scripts =
+  meson = mesonbuild.mesonmain:main
+
 [options.extras_require]
 progress =
   tqdm
 
+[options.packages.find]
+include = mesonbuild, mesonbuild.*
+exclude = *.data
+
 [tool:pytest]
 python_classes =
 python_files =
     run_unittests.py
-

setup.py

@@ -20,23 +20,12 @@ if sys.version_info < (3, 6):
     raise SystemExit('ERROR: Tried to install Meson with an unsupported Python version: \n{}'
                      '\nMeson requires Python 3.6.0 or greater'.format(sys.version))
 
-from mesonbuild.coredata import version
-from setuptools import setup, find_packages
+from setuptools import setup
 
-# On windows, will create Scripts/meson.exe and Scripts/meson-script.py
-# Other platforms will create bin/meson
-entries = {'console_scripts': ['meson=mesonbuild.mesonmain:main']}
 data_files = []
 if sys.platform != 'win32':
     # Only useful on UNIX-like systems
     data_files = [('share/man/man1', ['man/meson.1']),
                   ('share/polkit-1/actions', ['data/com.mesonbuild.install.policy'])]
 
-setup(name='meson',
-      version=version,
-      packages=find_packages(
-          include=['mesonbuild', 'mesonbuild.*'],
-          exclude=['*.data']
-      ),
-      entry_points=entries,
-      data_files=data_files,)
+setup(data_files=data_files,)