bpo-34225: Ensure INCLUDE and LIB directories do not end with a backslash. (GH-8464)

diff --git a/Lib/distutils/_msvccompiler.py b/Lib/distutils/_msvccompiler.py
index c9d3c6c..30b3b47 100644
--- a/Lib/distutils/_msvccompiler.py
+++ b/Lib/distutils/_msvccompiler.py
@@ -252,11 +252,11 @@
 
         for dir in vc_env.get('include', '').split(os.pathsep):
             if dir:
-                self.add_include_dir(dir)
+                self.add_include_dir(dir.rstrip(os.sep))
 
         for dir in vc_env.get('lib', '').split(os.pathsep):
             if dir:
-                self.add_library_dir(dir)
+                self.add_library_dir(dir.rstrip(os.sep))
 
         self.preprocess_options = None
         # If vcruntime_redist is available, link against it dynamically. Otherwise,