build: Expose absl as a dependency of webrtc-audio-processing

This is needed because the audio processing header references
abseil's optional.h. Clean up the declared dependencies while we're at
it.

Fixes: https://gitlab.freedesktop.org/pulseaudio/webrtc-audio-processing/-/merge_requests/34

meson.build

@@ -184,11 +184,20 @@ pkgconfig.generate(
     extra_cflags: [
       '-DWEBRTC_LIBRARY_IMPL',
     ] + platform_cflags,
-    libraries: libwebrtc_audio_processing,
+    libraries: [
+      libwebrtc_audio_processing,
+    ],
+    requires: [
+      # the audio processing header references absl's optional.h
+      'absl_base',
+    ]
 )
 
-audio_processing_dep = declare_dependency(link_with : libwebrtc_audio_processing,
+audio_processing_dep = declare_dependency(
-    include_directories : [webrtc_inc])
+  link_with: libwebrtc_audio_processing,
+  dependencies: [absl_dep],
+  include_directories: [webrtc_inc]
+)
 
 meson.override_dependency(apm_project_name, audio_processing_dep)
 
@@ -204,7 +213,9 @@ pkgconfig.generate(
     libraries: libwebrtc_audio_coding,
 )
 
-audio_coding_dep = declare_dependency(link_with : libwebrtc_audio_coding,
+audio_coding_dep = declare_dependency(
-    include_directories : [webrtc_inc])
+  link_with: libwebrtc_audio_coding,
+  include_directories: [webrtc_inc]
+)
 
 meson.override_dependency(ac_project_name, audio_coding_dep)

webrtc/modules/audio_coding/meson.build

@@ -45,12 +45,6 @@ libwebrtc_audio_coding = library(ac_project_name,
     install: true
 )
 
-webrtc_audio_coding_dep = declare_dependency(
-    link_with: libwebrtc_audio_coding,
-    include_directories: webrtc_inc,
-    version: ac_version
-)
-
 install_headers(['codecs/isac/bandwidth_info.h'],
     subdir: join_paths(include_subdir, 'modules', 'audio_coding', 'codecs', 'isac')
 )

webrtc/modules/audio_processing/meson.build

@@ -211,9 +211,3 @@ libwebrtc_audio_processing = library(apm_project_name,
     soversion: apm_minor_version,
     install: true
 )
-
-webrtc_audio_processing_dep = declare_dependency(
-    link_with: libwebrtc_audio_processing,
-    include_directories: webrtc_inc,
-    version: apm_version
-)