On a Debian 12/bookworm build machine that happened to have libsndio-dev installed, a Yocto build of qemu-system-native fails with

| ../qemu-7.2.0/audio/sndioaudio.c:18:10: fatal error: sndio.h: No such file or directory                                                                                                                                                                      
|    18 | #include <sndio.h>                                                                                                                                                                                                                                   

It seems this happens due to poky/meta/recipes-devtools/qemu/qemu.inc setting BHOST_PKGCONFIG_PATH and thereby including the host pkg-config path. pkg-config thus finds the host sndio (as can be verified in log.do_configure), but
pkg-config --cflags sndio
returns an empty line because sndio.h is located in the standard path /usr/include. This path is then not searched during the build, causing the error.
The same problem would probably happen for other qemu dependencies that have headers directly in /usr/include, not in a subdirectory.

Possible solutions:
- If BHOST_PKGCONFIG_PATH is really only for finding sdl, we could implement a way to limit the search in the host path to only that package.
- If it is intended that pkg-config should also find other dependencies in the host path, pkg-config could be called with the --keep-system-cflags option so it emits a -I/usr/include (but that may lead to more headers being taken from there than we intended...)
- If we now always build libsdl2-native instead of using the host library, the whole mechanism might also be removed.
- If we keep everything as it is, the documentation could also be extended to list "negative system requirements", i.e. removing all libraries qemu might depend on.