Disable warnings when compiling //net/third_party/nss/ssl on iOS.

net/third_party/nss/ssl/BUILD.gn

Index: net/third_party/nss/ssl/BUILD.gn
diff --git a/net/third_party/nss/ssl/BUILD.gn b/net/third_party/nss/ssl/BUILD.gn
index ee4449a187b173ad2e3410b822320dcbabf9d67f..1e43806bd06a423cc374812e5347a33d7569a202 100644
--- a/net/third_party/nss/ssl/BUILD.gn
+++ b/net/third_party/nss/ssl/BUILD.gn
@@ -100,6 +100,12 @@ component("libssl") {
     # There is a broken header guard in /usr/include/nss/secmod.h:
     # https://bugzilla.mozilla.org/show_bug.cgi?id=884072
     cflags = [ "-Wno-header-guard" ]
+
+    if (is_ios) {
+      # libssl uses routines deprecated on iOS (sem_init/sem_destroy).
+      # https://bugzilla.mozilla.org/show_bug.cgi?id=1192500
+      cflags += [ "-Wno-deprecated-declarations" ]
+    }
   }
 
   if (is_posix) {