diff --git a/Lib/distutils/command/build_ext.py b/Lib/distutils/command/build_ext.py
index dbcd9d1..274b1d8 100644
--- a/Lib/distutils/command/build_ext.py
+++ b/Lib/distutils/command/build_ext.py
@@ -219,7 +219,7 @@ class build_ext(Command):
         # For extensions under Cygwin, Python's library directory must be
         # appended to library_dirs
         if sys.platform[:6] == 'cygwin' or self.plat_name.startswith(('mingw')):
-            if sys.executable.startswith(os.path.join(sys.exec_prefix, "bin")):
+            if not sysconfig.python_build:
                 # building third party extensions
                 self.library_dirs.append(os.path.join(sys.prefix, "lib",
                                                       "python" + get_python_version(),