Handle -save-temps in collect2

Handle -save-temps in collect2

Handle the option, make the saved filenames and paths easier to handle.
Don't print '[Leaving...]' for files we never created and don't exist - or unless
verbose is true.

2018-12-23  Iain Sandoe  <iain@sandoe.co.uk>

	* collect2.c (main): Parse the output file early so we can make nicer
	temp names.  Respond to “-save-temps” in the GCC OPTIONS.
	(maybe_unlink): Don’t print “[Leaving…”] for files we never created
	and don’t exist.

From-SVN: r267370