Fix member alignment for all targets [PR103751].

Resolves:
PR testsuite/103751 - FAIL: gcc.dg/Warray-bounds-48.c (test for excess errors)

gcc/testsuite/ChangeLog:
	PR testsuite/103751
	* gcc.dg/Warray-bounds-48.c: Fix member alignment.

gcc/testsuite/gcc.dg/Warray-bounds-48.c

@@ -212,6 +212,7 @@ void test_a0 (struct A0 *p, unsigned n)
 struct A1
 {
   int32_t n;
+  __attribute__ ((aligned (4)))
   int16_t a1[1];    // { dg-message "while referencing 'a1'" }
 };