testsuite: vect: Fix gcc.dg/vect/vect-pr111779.c on SPARC [PR114072]

testsuite: vect: Fix gcc.dg/vect/vect-pr111779.c on SPARC [PR114072]

gcc.dg/vect/vect-pr111779.c FAILs on 32 and 64-bit Solaris/SPARC:

FAIL: gcc.dg/vect/vect-pr111779.c -flto -ffat-lto-objects  scan-tree-dump vect "LOOP VECTORIZED"
FAIL: gcc.dg/vect/vect-pr111779.c scan-tree-dump vect "LOOP VECTORIZED"

This patch implements Richard's analysis from the PR, skipping the
scan-tree-dump part for big-endian targets without vect_shift_char
support.

Tested on sparc-sun-solaris2.11 and i386-pc-solaris2.11 (32 and 64-bit each).

2024-05-22  Rainer Orth  <ro@CeBiTec.Uni-Bielefeld.DE>

	gcc/testsuite:
	PR tree-optimization/114072
	* gcc.dg/vect/vect-pr111779.c (scan-tree-dump): Require
	vect_shift_char on big-endian targets.