meson: declare spa_dep and override_dependency() for spa and pipewire

This allows meson subprojects (or projects using pipewire as a meson
subproject) to be able to use dependency('libpipewire-0.3') and
dependency('libspa-0.2') to find the uninstalled versions of these
libraries directly from the build dir instead of going through pkg-config

meson.build

@@ -1,7 +1,7 @@
 project('pipewire', ['c' ],
   version : '0.3.30',
   license : [ 'MIT', 'LGPL-2.1-or-later', 'GPL-2.0-only' ],
-  meson_version : '>= 0.49.0',
+  meson_version : '>= 0.54.0',
   default_options : [ 'warning_level=3',
                       'c_std=gnu99',
                       'b_pie=true',

spa/meson.build

@@ -44,9 +44,16 @@ if not get_option('examples').disabled()
   subdir('examples')
 endif
 
+spa_dep = declare_dependency(
+  include_directories : [spa_inc],
+  version : spaversion,
+)
+
 pkgconfig.generate(filebase : 'lib@0@'.format(spa_name),
   name : 'libspa',
   subdirs : spa_name,
   description : 'Simple Plugin API',
   version : spaversion,
   extra_cflags : '-D_REENTRANT')
+
+meson.override_dependency('lib@0@'.format(spa_name), spa_dep)

src/pipewire/meson.build

@@ -107,8 +107,8 @@ libpipewire = shared_library(pipewire_name, pipewire_sources,
 )
 
 pipewire_dep = declare_dependency(link_with : libpipewire,
-  include_directories : [pipewire_inc, configinc, spa_inc],
+  include_directories : [pipewire_inc, configinc],
-  dependencies : [pthread_lib, atomic_dep, ],
+  dependencies : [pthread_lib, atomic_dep, spa_dep],
 )
 
 pkgconfig.generate(libpipewire,
@@ -121,4 +121,6 @@ pkgconfig.generate(libpipewire,
   extra_cflags : '-D_REENTRANT',
   variables : ['moduledir=${libdir}/@0@'.format(pipewire_name)])
 
+meson.override_dependency('lib@0@'.format(pipewire_name), pipewire_dep)
+
 subdir('extensions')