Fix gcc 16 build.

TEST=local build
Bug: https://github.com/dart-lang/sdk/issues/63406
Change-Id: I20c2806e569211ef7d32e95961179dbf2aba15a9
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/505181
Reviewed-by: Alexander Markov <alexmarkov@google.com>
Commit-Queue: Ryan Macnak <rmacnak@google.com>

build/config/compiler/BUILD.gn

@@ -687,6 +687,7 @@ if (is_win) {
   } else {
     default_warning_flags += [
       "-Wno-ignored-qualifiers",  # Warnings in BoringSSL headers
+      "-Wno-stringop-overflow",  # ICU in gcc 16
     ]
     if (is_tsan && current_cpu == "riscv64") {
       default_warning_flags += [

runtime/vm/object_graph_copy.cc

@@ -1249,6 +1249,7 @@ class RetainingPath {
         // accommodate short chains Closure -> Context -> instance.
         saved_context_object_index = -1;
         saved_context_depth = -1;
+        USE(saved_context_depth);
       }
       // Add library url to the location if library is available.
       library = klass.library();

third_party/binaryen/BUILD.gn

@@ -28,6 +28,7 @@ config("binaryen_flags") {
     } else {
       # GCC
       cflags += [
+        "-Wno-array-bounds",
         "-Wno-dangling-pointer",
         "-Wno-deprecated",
         "-Wno-init-list-lifetime",