vulkan: include win32-specific header on windows

Needed for win32 handle code.
10 jobs for v1.7.0-rc4 in 1 minute and 59 seconds (queued for 1 second)
latest
Status Job ID Name Coverage
  Build
passed #243172
debian aarch64
build-debian-aarch64

00:00:33

passed #243173
macos
build-macos

00:00:04

passed #243168
debian amd64
build-ubuntu

00:00:23

15.0%
passed #243169
debian amd64
build-ubuntu-static

00:00:24

passed #243170
win32
build-win32

00:00:19

passed #243171
win64
build-win64

00:00:21

 
  Test
passed #243174
debian amd64
test-ubuntu-asan

00:00:22

passed #243175
debian amd64
test-ubuntu-msan

00:00:23

passed #243177
debian amd64
test-ubuntu-scan

00:00:47

passed #243176
debian amd64
test-ubuntu-ubsan

00:00:25