Add v8_os_page_size flag for cross compilation

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
index 1012182d42875d303a8aa16b46613daee5b12af7..9a21d33a867cd102e1451c9d7e00ec2e5a91382e 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -61,6 +61,9 @@ declare_args() {
   # Switches off inlining in V8.
   v8_no_inline = false
 
+  # Override OS page size when generating snapshot
+  v8_os_page_size = "0"
+
   # Similar to vfp but on MIPS.
   v8_can_use_fpu_instructions = true
 
@@ -679,6 +682,13 @@ action("run_mksnapshot") {
     ]
   }
 
+  if (v8_os_page_size != "0") {
+    args += [
+      "--v8_os_page_size",
+      v8_os_page_size,
+    ]
+  }
+
   if (v8_use_external_startup_data) {
     outputs += [ "$root_out_dir/snapshot_blob.bin" ]
     args += [