Use 16-byte stack alignment on 32-bit x86

We don't support AVX2 on x86-32 so having 32-byte alignment is redundant.
14 jobs for master in 5 minutes and 3 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Style
passed #245133
amd64 debian
style-check

00:00:21

 
  Build
passed #245134
amd64 debian
build-debian

00:00:31

passed #245139
debian aarch64
build-debian-aarch64

00:01:29

passed #245140
debian aarch64
build-debian-aarch64-clang-5

00:01:05

passed #245135
amd64 debian
build-debian-static

00:00:34

passed #245142
debian aarch64
build-debian-werror

00:00:31

passed #245136
amd64 debian
build-debian32

00:00:25

passed #245141
macos
build-macos

00:00:27

passed #245137
win32
build-win32

00:00:32

passed #245138
win64
build-win64

00:00:35

 
  Test
passed #245143
amd64 debian
test-debian

00:00:44

passed #245144
amd64 debian
test-debian-asan

00:02:06

passed #245145
amd64 debian
test-debian-msan

00:00:58

passed #245146
amd64 debian
test-debian-ubsan

00:01:19