testsuite: Fix gcc.dg/vect/pr101145* tests [PR101145]

I'm getting:
FAIL: gcc.dg/vect/pr101145.c scan-tree-dump-times vect "vectorized 1 loops" 7
FAIL: gcc.dg/vect/pr101145_1.c scan-tree-dump-times vect "vectorized 1 loops" 2
FAIL: gcc.dg/vect/pr101145_2.c scan-tree-dump-times vect "vectorized 1 loops" 2
FAIL: gcc.dg/vect/pr101145_3.c scan-tree-dump-times vect "vectorized 1 loops" 2
FAIL: gcc.dg/vect/pr101145.c -flto -ffat-lto-objects  scan-tree-dump-times vect "vectorized 1 loops" 7
FAIL: gcc.dg/vect/pr101145_1.c -flto -ffat-lto-objects  scan-tree-dump-times vect "vectorized 1 loops" 2
FAIL: gcc.dg/vect/pr101145_2.c -flto -ffat-lto-objects  scan-tree-dump-times vect "vectorized 1 loops" 2
FAIL: gcc.dg/vect/pr101145_3.c -flto -ffat-lto-objects  scan-tree-dump-times vect "vectorized 1 loops" 2
on i686-linux (or x86_64-linux with -m32/-mno-sse).
The problem is that those tests use dg-options, which in */vect/ testsuite
throws away all the carefully added default options to enable vectorization
on each target (and which e.g. vect_int etc. effective targets rely on).
The old way would be to name those tests gcc.dg/vect/O3-pr101145*,
but we can also use dg-additional-options (which doesn't throw the default
options, just appends to them) which is IMO better so that we don't have to
rename the tests.

2021-08-31  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/101145
	* gcc.dg/vect/pr101145.c: Use dg-additional-options with just -O3
	instead of dg-options with -O3 -fdump-tree-vect-details.
	* gcc.dg/vect/pr101145_1.c: Likewise.
	* gcc.dg/vect/pr101145_2.c: Likewise.
	* gcc.dg/vect/pr101145_3.c: Likewise.