change file SkParseColor.cpp
in folder:
/media/alex/data/Yocto/poky/build-rockchip/tmp/work/armv8a-poky-linux/qtwebengine/5.15.8+gitAUTOINC+73e76f9e86_48a205f9e0-r0/git/src/3rdparty/chromium/third_party/skia/src/utils

find mali_khrplatform.h and copy inside folder:
/media/alex/data/Yocto/poky/build-rockchip/tmp/work/armv8a-poky-linux/qtwebengine/5.15.8+gitAUTOINC+73e76f9e86_48a205f9e0-r0/recipe-sysroot/usr/include/KHR

create symbolic link inside KHR : khrplatform.h -> mali_khrplatform.h

then

bitbake qtwebengine:do_configure -f
bitbake qtwebengine:do_compile -f
to rebuild qtwebengine