This allows having the same directory structure for headers as it
is in $prefix/include when installed, so that we can build other
projects using pipewire uninstalled (via the -uninstalled.pc or
by using meson subprojects). Otherwise, external code that reasonably
includes <pipewire/extensions/foo.h> fails to compile.
Add an option to allow the user to disable examples, this will allow to
build pipewire without alsa. Without this option, build with
-Dpipewire-alsa=false -Dalsa=false fails on:
src/examples/meson.build:47:0: ERROR: Unknown variable "alsa_dep".
Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
