ipa: Do not emit info about temporary clones to ipa-clones dump (PR119852)

ipa: Do not emit info about temporary clones to ipa-clones dump (PR119852)

As described in PR 119852, the output of -fdump-ipa-clones can contain
"(null)" as the suffix/reason for cloning when we need to create a
clone to hold the original function during recursive inlining.  Such
clone is never output and so should not be part of the dump output
either.

gcc/ChangeLog:

2025-04-23  Martin Jambor  <mjambor@suse.cz>

	PR ipa/119852
	* cgraphclones.cc (dump_callgraph_transformation): Document the
	function.  Do not dump if suffix is NULL.

gcc/testsuite/ChangeLog:

2025-04-23  Martin Jambor  <mjambor@suse.cz>

	PR ipa/119852
	* gcc.dg/ipa/pr119852.c: New test.

(cherry picked from commit fb5829a01651d427a63a12c44ecc8baa47dbfc83)