Restore pythonlib support on older Pythons. Fixes pypa/distutils#9.

distutils/command/build_ext.py

@@ -16,6 +16,7 @@ from distutils.dep_util import newer_group
 from distutils.extension import Extension
 from distutils.util import get_platform
 from distutils import log
+from . import py37compat
 
 from site import USER_BASE
 
@@ -751,4 +752,4 @@ class build_ext(Command):
                 ldversion = get_config_var('LDVERSION')
                 return ext.libraries + ['python' + ldversion]
 
-        return ext.libraries
+        return ext.libraries + py37compat.pythonlib()

distutils/command/py37compat.py

+import sys
+
+
+def _pythonlib_compat():
+    """
+    On Python 3.7 and earlier, distutils would include the Python
+    library. See pypa/distutils#9.
+    """
+    from distutils import sysconfig
+    if not sysconfig.get_config_var('Py_ENABLED_SHARED'):
+        return
+
+    yield 'python{}.{}{}'.format(
+        sys.hexversion >> 24,
+        (sys.hexversion >> 16) & 0xff,
+        sysconfig.get_config_var('ABIFLAGS'),
+    )
+
+
+def compose(f1, f2):
+    return lambda *args, **kwargs: f1(f2(*args, **kwargs))
+
+
+pythonlib = (
+    compose(list, _pythonlib_compat)
+    if sys.version_info < (3, 8)
+    and sys.platform != 'darwin'
+    and sys.platform[:3] != 'aix'
+    else list
+)