Issue #3762: platform.architecture() fails if python is lanched via its symbolic link.

Reviewed Amaury Forgeot d'Arc (Backport of r66213)

Lib/platform.py

@@ -793,7 +793,7 @@ def _follow_symlinks(filepath):
     filepath = _abspath(filepath)
     while os.path.islink(filepath):
         filepath = os.path.normpath(
-            os.path.join(filepath,os.readlink(filepath)))
+            os.path.join(os.path.dirname(filepath),os.readlink(filepath)))
     return filepath
 
 def _syscmd_uname(option,default=''):