bug#48141: 28.0.50; Files left over by native compiler

[Gregory Heytings]

> > I have a few files apparently left over from failed native 
> > compilations. They look like `lisp/foo.elcABCDEF` where `ABCDEF` is 
> > random (presumably chosen by `make-temp-file`).
>
> This is not directly related to native compilation. This is so creation 
> of .elc files can be atomic (bug#4196).
>
> > and maybe we should put them in /tmp?
>
> IIUC, the temp files must be on the same partition as the destination 
> .elc files, else the move would not be atomic.

Given that requirement (atomicity) and its implication (same partition), 
would it not be better to create these temporary files in a 'tmp' 
subdirectory of their target directory (e.g. 'lisp/tmp' for el files in 
'lisp' and 'lisp/calc/tmp' for el files in 'lisp/calc') instead of using 
random filenames in the target directory itself?