Move warning suppression flag to default_warnings config

It seems like the was accidentally added to the treat_warnings_as_errors
config instead of the regular suppression config, so the warning was
turned back on for some local builds where that gn arg was disabled.
Move it to the normal place for warning suppressions.

[email protected]

Bug: 427702057
Change-Id: I28c532071d627a9d98375e7b6e8806bdcf5fa4f1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6681120
Reviewed-by: Hans Wennborg <[email protected]>
Auto-Submit: Devon Loehr <[email protected]>
Commit-Queue: Devon Loehr <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1479887}
NOKEYCHECK=True
GitOrigin-RevId: 5fef29d673d43a3cb833087a886638dc7a4746f3

Author: DKLoehr

config/compiler/BUILD.gn

@@ -1826,8 +1826,7 @@ config("libcxx_module") {
     ]
 
     if (is_linux || is_chromeos) {
-      sysroot_modulemap =
-          rebase_path(SYSROOT_MODULEMAP, root_build_dir)
+      sysroot_modulemap = rebase_path(SYSROOT_MODULEMAP, root_build_dir)
 
       cflags_cc += [ "-fmodule-map-file=" + sysroot_modulemap ]
     }
@@ -1924,9 +1923,6 @@ config("treat_warnings_as_errors") {
   # Note we apply the actual lint flags in config("compiler"). All warnings
   # are suppressed in third-party crates.
   rustflags = [ "-Dwarnings" ]
-
-  # TODO(crbug.com/424424323): Clean up and enable.
-  rustflags += [ "-Amismatched_lifetime_syntaxes" ]
 }
 
 # tot_warnings ----------------------------------------------------------------
@@ -2168,6 +2164,9 @@ config("default_warnings") {
   # an error by default eventually; see
   # https://github.com/rust-lang/rust/issues/71668
   rustflags = [ "-Dunsafe_op_in_unsafe_fn" ]
+
+  # TODO(crbug.com/424424323): Clean up and enable.
+  rustflags += [ "-Amismatched_lifetime_syntaxes" ]
 }
 
 # prevent_unsafe_narrowing ----------------------------------------------------