avoid file ownership requirement in touch (#28819)

Using `futimes` and passing NULL for the `times` parameter sets the current and access file times, but does not require file ownwership.

From man page:
> If times is NULL, the access and modification times are set to the current time. The caller must be the owner of the file, have permission to write the file, or be the superuser.

base/file.jl

@@ -403,8 +403,13 @@ We can see the [`mtime`](@ref) has been modified by `touch`.
 function touch(path::AbstractString)
  f = open(path, JL_O_WRONLY | JL_O_CREAT, 0o0666)
  try
- t = time()
- futime(f,t,t)
+ if Sys.isunix()
+ ret = ccall(:futimes, Cint, (Cint, Ptr{Cvoid}), fd(f), C_NULL)
+ systemerror(:futimes, ret != 0, extrainfo=path)
+ else
+ t = time()
+ futime(f,t,t)
+ end
  finally
  close(f)
  end