[gn] Switch more linux32 bots to gn

gni/v8.gni

Index: gni/v8.gni
diff --git a/gni/v8.gni b/gni/v8.gni
index fb36239300f41b5b03e04358cb985032bd790365..93b766920a7c71bfc7e10d1b36fea5902390a8f5 100644
--- a/gni/v8.gni
+++ b/gni/v8.gni
@@ -22,7 +22,13 @@ declare_args() {
 
   # Use external files for startup data blobs:
   # the JS builtins sources and the start snapshot.
-  v8_use_external_startup_data = !is_ios
+  v8_use_external_startup_data = ""
+}
+
+if (v8_use_external_startup_data == "") {
+  # If not specified as a gn arg, use external startup data by default if
+  # a snapshot is used and if we're not on ios.
+  v8_use_external_startup_data = v8_use_snapshot && !is_ios
 }
 
 ###############################################################################