diff -rupN --no-dereference Python-3.10.0rc1/Lib/distutils/sysconfig.py Python-3.10.0rc1-new/Lib/distutils/sysconfig.py
--- Python-3.10.0rc1/Lib/distutils/sysconfig.py	2021-08-04 16:36:58.970361746 +0200
+++ Python-3.10.0rc1-new/Lib/distutils/sysconfig.py	2021-08-04 16:36:59.191359517 +0200
@@ -182,6 +182,17 @@ def parse_makefile(fn, g=None):
 # Following functions are deprecated together with this module and they
 # have no direct replacement
 
+def _posix_build():
+    # GCC[mingw*] use posix build system
+    # Check for cross builds explicitly
+    host_platform = os.environ.get("_PYTHON_HOST_PLATFORM")
+    if host_platform:
+        if host_platform.startswith('mingw'):
+            return True
+    return os.name == 'posix' or \
+        (os.name == "nt" and 'GCC' in sys.version)
+posix_build = _posix_build()
+
 # Calculate the build qualifier flags if they are defined.  Adding the flags
 # to the include and lib directories only makes sense for an installation, not
 # an in-source build.
@@ -279,7 +290,7 @@ def get_python_inc(plat_specific=0, pref
     """
     if prefix is None:
         prefix = plat_specific and BASE_EXEC_PREFIX or BASE_PREFIX
-    if os.name == "posix":
+    if posix_build:
         if python_build:
             # Assume the executable is in the build directory.  The
             # pyconfig.h file should be in the same directory.  Since
@@ -326,7 +337,7 @@ def get_python_lib(plat_specific=0, stan
         else:
             prefix = plat_specific and EXEC_PREFIX or PREFIX
 
-    if os.name == "posix":
+    if posix_build:
         if plat_specific or standard_lib:
             # Platform-specific modules (any module from a non-pure-Python
             # module distribution) or standard Python library modules.
diff -rupN --no-dereference Python-3.10.0rc1/Lib/site.py Python-3.10.0rc1-new/Lib/site.py
--- Python-3.10.0rc1/Lib/site.py	2021-08-02 21:53:59.000000000 +0200
+++ Python-3.10.0rc1-new/Lib/site.py	2021-08-04 16:36:59.191359517 +0200
@@ -273,7 +273,8 @@ def _getuserbase():
     def joinuser(*args):
         return os.path.expanduser(os.path.join(*args))
 
-    if os.name == "nt":
+    from sysconfig import _POSIX_BUILD
+    if os.name == "nt" and not _POSIX_BUILD:
         base = os.environ.get("APPDATA") or "~"
         return joinuser(base, "Python")
 
@@ -288,7 +289,8 @@ def _getuserbase():
 def _get_path(userbase):
     version = sys.version_info
 
-    if os.name == 'nt':
+    from sysconfig import _POSIX_BUILD
+    if sys.platform == 'win32' and not _POSIX_BUILD:
         ver_nodot = sys.winver.replace('.', '')
         return f'{userbase}\\Python{ver_nodot}\\site-packages'
 
@@ -356,6 +358,7 @@ def getsitepackages(prefixes=None):
     if prefixes is None:
         prefixes = PREFIXES
 
+    from sysconfig import _POSIX_BUILD
     for prefix in prefixes:
         if not prefix or prefix in seen:
             continue
@@ -365,7 +368,7 @@ def getsitepackages(prefixes=None):
         if sys.platlibdir != "lib":
             libdirs.append("lib")
 
-        if os.sep == '/':
+        if _POSIX_BUILD:
             for libdir in libdirs:
                 path = os.path.join(prefix, libdir,
                                     "python%d.%d" % sys.version_info[:2],
diff -rupN --no-dereference Python-3.10.0rc1/Lib/sysconfig.py Python-3.10.0rc1-new/Lib/sysconfig.py
--- Python-3.10.0rc1/Lib/sysconfig.py	2021-08-04 16:36:59.188359547 +0200
+++ Python-3.10.0rc1-new/Lib/sysconfig.py	2021-08-04 16:36:59.191359517 +0200
@@ -5,6 +5,10 @@ import sys
 import textwrap
 from os.path import pardir, realpath
 
+# GCC[mingw*] use posix build system
+_POSIX_BUILD = os.name == 'posix' or \
+    (os.name == "nt" and 'GCC' in sys.version)
+
 __all__ = [
     'get_config_h_filename',
     'get_config_var',
@@ -74,7 +78,7 @@ 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")
 
@@ -137,7 +141,6 @@ _variable_rx = r"([a-zA-Z][a-zA-Z0-9_]+)
 _findvar1_rx = r"\$\(([A-Za-z][A-Za-z0-9_]*)\)"
 _findvar2_rx = r"\${([A-Za-z][A-Za-z0-9_]*)}"
 
-
 def _safe_realpath(path):
     try:
         return realpath(path)
@@ -226,7 +229,7 @@ def _expand_vars(scheme, vars):
 
 
 def _get_preferred_schemes():
-    if os.name == 'nt':
+    if os.name == 'nt' and not _POSIX_BUILD:
         return {
             'prefix': 'nt',
             'home': 'posix_home',
@@ -552,7 +555,7 @@ def parse_config_h(fp, vars=None):
 def get_config_h_filename():
     """Return the path of pyconfig.h."""
     if _PYTHON_BUILD:
-        if os.name == "nt":
+        if os.name == "nt" and not _POSIX_BUILD:
             inc_dir = os.path.join(_sys_home or _PROJECT_BASE, "PC")
         else:
             inc_dir = _sys_home or _PROJECT_BASE
@@ -628,9 +631,9 @@ def get_config_vars(*args):
         except AttributeError:
             _CONFIG_VARS['py_version_nodot_plat'] = ''
 
-        if os.name == 'nt':
+        if os.name == 'nt' and not _POSIX_BUILD:
             _init_non_posix(_CONFIG_VARS)
-        if os.name == 'posix':
+        if _POSIX_BUILD:
             _init_posix(_CONFIG_VARS)
         # For backward compatibility, see issue19555
         SO = _CONFIG_VARS.get('EXT_SUFFIX')
@@ -644,7 +647,7 @@ def get_config_vars(*args):
 
         # Always convert srcdir to an absolute path
         srcdir = _CONFIG_VARS.get('srcdir', _PROJECT_BASE)
-        if os.name == 'posix':
+        if _POSIX_BUILD:
             if _PYTHON_BUILD:
                 # If srcdir is a relative path (typically '.' or '..')
                 # then it should be interpreted relative to the directory