setup: Reuse golang.pyx.build to build DSOs

We already reuse golang.pyx.build in setup.py to build Extensions, but
DSOs were built via setuptools_dso directly so far. To support Windows
we will soon need to adjust compilation flags for both Extensions and
DSOs. It makes sense to first concentrate build recipes in one place
before doing that.

-> Move/factor DSOs build flags into golang.pyx.build and reuse that
from setup.

golang/pyx/build.py

-# Copyright (C) 2019-2022  Nexedi SA and Contributors.
+# Copyright (C) 2019-2023  Nexedi SA and Contributors.
 #                          Kirill Smelkov <kirr@nexedi.com>
 #
 # This program is free software: you can Use, Study, Modify and Redistribute
@@ -128,14 +128,14 @@ def setup(**kw):
 #       x_dsos = [DSO('mypkg.mydso', ['mypkg/mydso.cpp'])],
 #   )
 def DSO(name, sources, **kw):
-    _, kw = _with_build_defaults(kw)
+    _, kw = _with_build_defaults(name, kw)
     dso = setuptools_dso.DSO(name, sources, **kw)
     return dso
 
 
 # _with_build_defaults returns copy of kw amended with build options common for
 # both DSO and Extension.
-def _with_build_defaults(kw):   # -> (pygo, kw')
+def _with_build_defaults(name, kw):   # -> (pygo, kw')
     # find pygolang root
     gopkg = _findpkg("golang")
     pygo  = dirname(gopkg.path) # .../pygolang/golang -> .../pygolang
@@ -149,10 +149,11 @@ def _with_build_defaults(kw):   # -> (pygo, kw')
     incv.insert(0, pygo)
     kw['include_dirs'] = incv
 
-    # link with libgolang.so
-    dsov = kw.get('dsos', [])[:]
-    dsov.insert(0, 'golang.runtime.libgolang')
-    kw['dsos'] = dsov
+    # link with libgolang.so  if it is not libgolang itself
+    if name != 'golang.runtime.libgolang':
+        dsov = kw.get('dsos', [])[:]
+        dsov.insert(0, 'golang.runtime.libgolang')
+        kw['dsos'] = dsov
 
     # default language to C++ (chan[T] & co are accessible only via C++)
     lang = kw.setdefault('language', 'c++')
@@ -160,7 +161,11 @@ def _with_build_defaults(kw):   # -> (pygo, kw')
     # default to C++11 (chan[T] & co require C++11 features)
     ccdefault = []
     if lang == 'c++':
-        ccdefault.append('-std=c++11')
+        if name == 'golang.runtime.libgolang':
+            ccdefault.append('-std=gnu++11') # not c++11 as linux/list.h uses typeof
+        else:
+            ccdefault.append('-std=c++11')
+
     # default to no strict-aliasing
     ccdefault.append('-fno-strict-aliasing')
 
@@ -203,7 +208,7 @@ def _with_build_defaults(kw):   # -> (pygo, kw')
 #       ext_modules = [Extension('mypkg.mymod', ['mypkg/mymod.pyx'])],
 #   )
 def Extension(name, sources, **kw):
-    pygo, kw = _with_build_defaults(kw)
+    pygo, kw = _with_build_defaults(name, kw)
 
     # some pyx-level depends to workaround a bit lack of proper dependency
     # tracking in setuptools/distutils.

setup.py

@@ -19,10 +19,6 @@
 # See https://www.nexedi.com/licensing for rationale and options.
 
 from setuptools import find_packages
-# setuptools has Library but this days it is not well supported and test for it
-# has been killed https://github.com/pypa/setuptools/commit/654c26f78a30
-# -> use setuptools_dso instead.
-from setuptools_dso import DSO
 from setuptools.command.install_scripts import install_scripts as _install_scripts
 from setuptools.command.develop import develop as _develop
 from distutils import sysconfig
@@ -34,13 +30,13 @@ def readfile(path):
     with open(path, 'r') as f:
         return f.read()
 
-# reuse golang.pyx.build to build pygolang extensions.
+# reuse golang.pyx.build to build pygolang dso and extensions.
 # we have to be careful and inject synthetic golang package in order to be
 # able to import golang.pyx.build without built/working golang.
 trun = {}
 exec(readfile('trun'), trun)
 trun['ximport_empty_golangmod']()
-from golang.pyx.build import setup, Extension as Ext
+from golang.pyx.build import setup, DSO, Extension as Ext
 
 
 # grep searches text for pattern.
@@ -223,19 +219,16 @@ setup(
                             'golang/strings.h',
                             'golang/sync.h',
                             'golang/time.h'],
-                        include_dirs    = ['.', '3rdparty/include'],
+                        include_dirs    = ['3rdparty/include'],
                         define_macros   = [('BUILDING_LIBGOLANG', None)],
-                        extra_compile_args = ['-std=gnu++11'], # not c++11 as linux/list.h uses typeof
                         soversion       = '0.1'),
 
                     DSO('golang.runtime.libpyxruntime',
                         ['golang/runtime/libpyxruntime.cpp'],
                         depends = ['golang/pyx/runtime.h'],
-                        include_dirs    = ['.', sysconfig.get_python_inc()],
+                        include_dirs    = [sysconfig.get_python_inc()],
                         define_macros   = [('BUILDING_LIBPYXRUNTIME', None)],
-                        extra_compile_args = ['-std=c++11'],
-                        soversion       = '0.1',
-                        dsos = ['golang.runtime.libgolang'])],
+                        soversion       = '0.1')],
 
     ext_modules = [
                     Ext('golang._golang',