- Sync -std= with devel/abseil to match ABI

--- meson.build.orig	2020-12-12 16:13:37 UTC
+++ meson.build
@@ -4,7 +4,7 @@ project('webrtc-audio-processing-1', 'c', 'cpp',
   default_options : [ 'warning_level=1',
                       'buildtype=debugoptimized',
                       'c_std=c11',
-                      'cpp_std=c++14',
+                      'cpp_std=c++17',
                     ]
 )