Customize site for MINGW

Co-authored-by: Алексей <alexey.pawlow@gmail.com>
Co-authored-by: Christoph Reiter <reiter.christoph@gmail.com>

Author: Alexpux

Lib/site.py

@@ -88,6 +88,12 @@
 USER_BASE = None
 
 
+# Same as defined in Lib/sysconfig.py
+# redeclared since sysconfig is large for site.
+# GCC[mingw*] use posix build system
+_POSIX_BUILD = os.name == 'posix' or \
+    (os.name == "nt" and 'GCC' in sys.version)
+
 def _trace(message):
     if sys.flags.verbose:
         print(message, file=sys.stderr)
@@ -273,7 +279,7 @@ def _getuserbase():
     def joinuser(*args):
         return os.path.expanduser(os.path.join(*args))
 
-    if os.name == "nt":
+    if os.name == "nt" and not _POSIX_BUILD:
         base = os.environ.get("APPDATA") or "~"
         return joinuser(base, "Python")
 
@@ -288,7 +294,7 @@ def joinuser(*args):
 def _get_path(userbase):
     version = sys.version_info
 
-    if os.name == 'nt':
+    if os.name == 'nt' and not _POSIX_BUILD:
         ver_nodot = sys.winver.replace('.', '')
         return f'{userbase}\\Python{ver_nodot}\\site-packages'
 
@@ -361,7 +367,7 @@ def getsitepackages(prefixes=None):
             continue
         seen.add(prefix)
 
-        if os.sep == '/':
+        if _POSIX_BUILD:
             libdirs = [sys.platlibdir]
             if sys.platlibdir != "lib":
                 libdirs.append("lib")