revert patch to ensurepip and instead patch platform.libc_ver to give up when we cannot open the executable

Author: timfel

graalpython/lib-python/3/ensurepip/__init__.py

@@ -23,14 +23,6 @@ def _run_pip(args, additional_paths=None):
     if additional_paths is not None:
         sys.path = additional_paths + sys.path
 
-    # Truffle patch: begin
-    import platform
-
-    def libc_ver(executable=sys.executable, lib='', version='', chunksize=16384):
-        return lib, None
-    setattr(platform, 'libc_ver', libc_ver)
-    # End Truffle patch
-
     # Install the bundled software
     import pip._internal
     return pip._internal.main(args)

graalpython/lib-python/3/platform.py

@@ -161,6 +161,9 @@ def libc_ver(executable=sys.executable, lib='', version='',
         The file is read and scanned in chunks of chunksize bytes.
 
     """
+    if sys.implementation.name == "graalpython":
+        if executable == sys.executable and not os.path.exists(executable):
+            return lib, version
     if hasattr(os.path, 'realpath'):
         # Python 2.2 introduced os.path.realpath(); it is used
         # here to work around problems with Cygwin not being