Move testcase gcc.dg/tree-ssa/pr93776.c to gcc.c-torture/compile/pr93776.c

Since this testcase is not exactly SSA specific and it would
be a good idea to compile this at more than just at -O1, moving
it to gcc.c-torture/compile would do that.

Committed as obvious after a test on x86_64-linux-gnu.

gcc/testsuite/ChangeLog:

	* gcc.dg/tree-ssa/pr93776.c: Moved to...
	* gcc.c-torture/compile/pr93776.c: ...here.

gcc/testsuite/gcc.dg/tree-ssa/pr93776.c → gcc/testsuite/gcc.c-torture/compile/pr93776.c

-/* { dg-do compile } */
-/* { dg-options "-O1" } */
+/* This used to ICE in SRA as SRA got
+   confused by the zero signed assigment. */
 
 struct empty {};
 struct s { int i; };