backport: PR tree-optimization/90989 - incorrrect strlen result after second strcpy

backport: PR tree-optimization/90989 - incorrrect strlen result after second strcpy

Backport from mainline

PR tree-optimization/90989 - incorrrect strlen result after second strcpy
	into the same destination

gcc/ChangeLog:

	PR tree-optimization/90989
	* tree-ssa-strlen.c (handle_char_store): Constrain a single character
	optimization to just single character stores.

gcc/testsuite/ChangeLog:

	PR tree-optimization/90989
	* gcc.dg/strlenopt-26.c: Exit with test result status.
	* gcc.dg/strlenopt-67.c: New test.

From-SVN: r274021