Hooks: distutils: Fix no suitable dest location found for pyconfig.h.

Locating `pyconfig.h` and the `makefile` gets into a mess when using
certain environment managers (pyenv-virtualenv) because PyInstaller,
whilst trying to find an appropriate `dest` path to put the files in,
gets confused by `sys.prefix` (or its varients) not being a parent dir of
the config and makefiles. As a (seemingly more rubust) alternative, this
commit uses `sysconfig.get_python_inc(prefix=".")` to choose a dest dir
instead. See pyinstaller#5018.

PyInstaller/hooks/hook-distutils.py

@@ -17,19 +17,42 @@
 runtime for platform-specific metadata.
 """
 
-# TODO Verify that bundling Makefile and pyconfig.h is still required for Python 3.
-
-import os
-import sysconfig
-
-from PyInstaller.utils.hooks import relpath_to_config_or_make
-
-_CONFIG_H = sysconfig.get_config_h_filename()
-_MAKEFILE = sysconfig.get_makefile_filename()
-
-# Data files in PyInstaller hook format.
-datas = [(_CONFIG_H, relpath_to_config_or_make(_CONFIG_H))]
-
-# The Makefile does not exist on all platforms, eg. on Windows
-if os.path.exists(_MAKEFILE):
-    datas.append((_MAKEFILE, relpath_to_config_or_make(_MAKEFILE)))
+from distutils import sysconfig
+import sys
+from os import path
+
+from PyInstaller.utils.hooks import logger
+
+
+if sys.version_info < (3, 6):
+    # XXX: Pythons >= 3.6 no longer use these files. Once we drop 3.5 support
+    # we can delete this.
+
+    datas = []
+
+    # Locate the ``Include`` folder containing the two files.
+    INCLUDE = sysconfig.get_python_inc()
+    # Get a dist target location. This seems to handle venv and its many
+    # variants better than our own attempts involving ``sys.prefix``. See
+    # https://github.com/pyinstaller/pyinstaller/issues/4775.
+    DEST = sysconfig.get_python_inc(prefix=".")
+
+    for filename in ["pyconfig.h", "Makefile"]:
+        source = path.join(INCLUDE, filename)
+        if path.exists(source):
+            datas.append((source, DEST))
+            logger.debug("Add '{}' from '{}' to '{}'."
+                         .format(filename, INCLUDE, DEST))
+        else:
+            logger.debug("Skip non-existent '{}' from '{}' to '{}'."
+                         .format(filename, INCLUDE, DEST))
+
+else:
+    # In Python 3.6 and later ``distutils.sysconfig`` takes on the same
+    # behaviour as regular ``sysconfig`` of moving the config vars to an
+    # extension module (see hook-sysconfig.py). But it doesn't use a nice
+    # `get extension module name` function like ``sysconfig`` does. However the
+    # extension module is the same file that ``sysconfig`` uses so if we run
+    # the hook for ``sysconfig``, the extension module will be located and
+    # included.
+    hiddenimports = ["sysconfig"]

news/5218.hooks.rst

@@ -0,0 +1 @@
+Update hook for ``distutils.sysconfig`` to be compatible with pyenv-virtualenv.