Update semantic_interposition flag at analysis time

This patch solves problem with FE first finalizing function and then adding
-fno-semantic-interposition flag (by parsing optimization attribute).

gcc/ChangeLog:

2022-04-09  Jan Hubicka  <hubicka@ucw.cz>

	PR ipa/103376
	* cgraphunit.cc (cgraph_node::analyze): update semantic_interposition
	flag.

gcc/testsuite/ChangeLog:

2022-04-09  Jan Hubicka  <hubicka@ucw.cz>

	PR ipa/103376
	* gcc.c-torture/compile/pr103376.c: New test.