Use "-Os" for Android or IOS in "optimize_max" config

build/config/compiler/BUILD.gn

Index: build/config/compiler/BUILD.gn
diff --git a/build/config/compiler/BUILD.gn b/build/config/compiler/BUILD.gn
index 91f40810a826672c7062fc11c551e267711e51c6..3820ca57284e2037546b0da996d321ce512f8f0f 100644
--- a/build/config/compiler/BUILD.gn
+++ b/build/config/compiler/BUILD.gn
@@ -1409,7 +1409,11 @@ config("optimize_max") {
         ]
       }
     } else {
-      cflags = [ "-O2" ] + common_optimize_on_cflags
+      if (optimize_for_size) {
+        cflags = [ "-Os" ] + common_optimize_on_cflags
+      } else {
+        cflags = [ "-O2" ] + common_optimize_on_cflags
+      }
     }
   }
 }