Prevent jsoncpp from hiding deprecated declarations in WebRTC

Bug: chromium:983223
Change-Id: I7959383f9ca5149df39eb66c2b54d6e4fd27f534
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/258241
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Commit-Queue: Florent Castelli <orphis@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#36522}
diff --git a/.gn b/.gn
index 75872e3..aea8f2c 100644
--- a/.gn
+++ b/.gn
@@ -65,4 +65,7 @@
 
   # Differently from Chromium, WebRTC still support SDK 21.
   default_min_sdk_version = 21
+
+  # Prevent jsoncpp to pass -Wno-deprecated-declarations to users
+  jsoncpp_no_deprecated_declarations = false
 }