[fuchsia] Add API target level default value

Bug: chromium:1357478
Change-Id: I6c412efa9ecc57fd8fbd47a5753c7731558df3b1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3859353Reviewed-by: Wez <wez@chromium.org>
Commit-Queue: Victor Gomes <victorgomes@chromium.org>
Auto-Submit: Victor Gomes <victorgomes@chromium.org>
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/main@{#82784}

.gn

@@ -24,6 +24,12 @@ no_check_targets = [
   "//third_party/icu:*",
 ]
 
+default_args = {
+  # Overwrite default args declared in the Fuchsia sdk
+  # Please maintain this in sync with Chromium version in src/.gn
+  fuchsia_target_api_level = 9
+}
+
 # These are the list of GN files that run exec_script. This whitelist exists
 # to force additional review for new uses of exec_script, which is strongly
 # discouraged except for gypi_to_gn calls.