Add an alternative testcase for PR 70740

While looking into improving phiprop, I noticed that
the current pr70740.c testcase was being optimized almost
all the way before phiprop because the addresses were considered
the same; the arrays were all zero in size.

This adds an alternative testcase which changes the array sizes to be 1
and phiprop can and will act on this testcase now and the fix which was
being tested is actually tested now.

Tested on x86_64-linux-gnu.

	PR tree-optimization/70740

gcc/testsuite/ChangeLog:

	* gcc.dg/torture/pr70740-1.c: New test.

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