Upstream patch `patch-getpath-use-base_executable-for-executable_dir.patch`

[jjhelmus]

patch-getpath-use-base_executable-for-executable_dir.patch
patch-getpath-use-base_executable-for-executable_dir-314.patch

When reading inside a venv use the base_executable path to determine executable_dir when valid. This allows venv to be created from symlinks.

c.f. #896

[brettcannon]

I think this is okay.