BoardConfig.mk: build fix

Removes the call to inherit-product-if-exists in BoardConfig.mk
since it breaks the build and does not belong here.
gralloc.h: build fix

Fixes building by #ifndef guarding a possible double declaration of
GRALLOC_MODULE_PERFORM_CREATE_HANDLE_FROM_BUFFER in our local gralloc.h.

The file is included a few times and in the case when it is called from
hardware/qcom/display/libgralloc/gralloc_priv.h,
GRALLOC_MODULE_PERFORM_CREATE_HANDLE_FROM_BUFFER is already defined
there, leading to a double declaration.  However, this definition is
needed by other parts in the code so we can not simply remove it, but
instead guard the definition with #ifndef that skips it only when the
file is included from gralloc_priv.h.
libcamera: build fix

Allows the buzz camera to be build by using a dummy intermediate
export_includes file. Since we use a proprietary libcamera, there is
nothing that gets built, so normally no respective export_includes file
is created. Using an empty file, the build can go on.
buzz: wifi fix

Fixes the wifi for the buzz by using the (old) ICS module and
overwriting the wpa_supplicant.conf file with our own version.
Also sets the /dev/rfkill permissions as in arco's buzz repo.
buzz: audio fix

Fixes the audio of the buzz by updating the respective Android.mk files
to actually run the libaudio build.