Add -Wstrict-aliasing to vector-struct-1.C testcase

As noticed by Marek Polacek in https://gcc.gnu.org/pipermail/gcc-patches/2024-February/645836.html

,
this testcase was not failing before without -Wstrict-aliasing so let's add that option.

Committed as obvious after testing to make sure the test is now testing with `-Wstrict-aliasing` and `-flto`.

gcc/testsuite/ChangeLog:

	* g++.dg/torture/vector-struct-1.C: Add -Wstrict-aliasing.

Signed-off-by: Andrew Pinski <quic_apinski@quicinc.com>

gcc/testsuite/g++.dg/torture/vector-struct-1.C

+/* { dg-options "-Wstrict-aliasing" } */
 /* PR c++/97990 */
 /* This used to crash with lto and strict aliasing enabled as the
    vector type variant still had TYPE_ALIAS_SET set on it. */