With -no-vulkan option vulkan headers is using

configure -prefix install -opensource -confirm-license --recheck-all -shared -release -c++std c++11 -mp -nomake tests -nomake examples -nomake tools -platform win32-msvc2019 -skip qtscript -skip qtsensors -skip qttools -webengine-pepper-plugins -webengine-proprietary-codecs -no-webengine-webrtc -opengl dynamic -no-vulkan -no-feature-vulkan --prefix=C:\Exts\qt_560\build_x32 -openssl-linked -IC:\Exts\qt_560\reqs_openssl_x32_static\include -LC:\Exts\qt_560\reqs_openssl_x32_static\lib -IC:\Exts\qt_560\reqs_zlib_x32_static\include -LC:\Exts\qt_560\reqs_zlib_x32_static\lib

C:\Exts\qt_560\reqs_jom_x32_static\jom.exe -f Makefile.Release
call C:\Exts\qt_560\qtbase\src\gui\qvkgen_wrapper.bat vulkan\vk.xml C:/Exts/qt_560/qtbase/header.LGPL vulkan/qvulkanfunctions
C:\Exts\qt_560\qtbase\bin\rcc.exe -name qpdf painting\qpdf.qrc -o .rcc\release\qrc_qpdf.cpp
C:\Exts\qt_560\qtbase\bin\rcc.exe -name qmake_webgradients .rcc\release\qmake_webgradients.qrc -o .rcc\release\qrc_qmake_webgradients.cpp
jom: C:\Exts\qt_560\qtbase\src\gui\Makefile.Release [vulkan\qvulkanfunctions.h] Error 2
jom: C:\Exts\qt_560\qtbase\src\gui\Makefile.Release [.rcc\release\qrc_qpdf.cpp] Error 2
jom: C:\Exts\qt_560\qtbase\src\gui\Makefile.Release [.rcc\release\qrc_qmake_webgradients.cpp] Error 2
jom: C:\Exts\qt_560\qtbase\src\gui\Makefile [release] Error 2
jom: C:\Exts\qt_560\qtbase\src\Makefile [sub-gui-make_first] Error 2
jom: C:\Exts\qt_560\qtbase\Makefile [sub-src-make_first] Error 2
jom: C:\Exts\qt_560\Makefile [module-qtbase-make_first] Error 2