tree-optimization/105080 - make sure SCEV is available for ranger

When doing format diagnostics at -O0 we should make sure to make
SCEV available to avoid false positives due to ranges we otherwise
can trivially compute.

2022-03-28  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/105080
	* tree-ssa-strlen.cc (printf_strlen_execute): Always init
	loops and SCEV.

	* gcc.dg/pr105080.c: New testcase.