This commit replaces `os.Setenv` with `t.Setenv` in tests. The
environment variable is automatically restored to its original value
when the test and all its subtests complete.
Reference: https://pkg.go.dev/testing#T.Setenv
Signed-off-by: Eng Zer Jun <engzerjun@gmail.com>
Signed-off-by: Eng Zer Jun <engzerjun@gmail.com>
We need to use `os.Lstat` instead of `os.Stat` if we are going to
manually inspect files for whether they are a symlink. On macOS, it
looks like `os.Stat` returns information about the symlink itself.
