Switch all buildbots to GN build

scripts/slave/recipes/pdfium.expected/linux_xfa_rel.json

Index: scripts/slave/recipes/pdfium.expected/linux_xfa_rel.json
diff --git a/scripts/slave/recipes/pdfium.expected/linux_xfa_rel.json b/scripts/slave/recipes/pdfium.expected/linux_xfa_rel.json
index 543e5eb642e115c74d7a98006a97ec4ab4765f9a..bbfd8cc85c469bafbed7b80ce4050b9b519631af 100644
--- a/scripts/slave/recipes/pdfium.expected/linux_xfa_rel.json
+++ b/scripts/slave/recipes/pdfium.expected/linux_xfa_rel.json
@@ -55,6 +55,7 @@
     ],
     "cwd": "[SLAVE_BUILD]/pdfium",
     "env": {
+      "GYP_PDFIUM_NO_ACTION": "1",
       "GYP_DEFINES": "pdf_enable_v8=1 pdf_enable_xfa=1",
       "PATH": "%(PATH)s:RECIPE_PACKAGE_REPO[depot_tools]"
     },
@@ -62,6 +63,19 @@
   },
   {
     "cmd": [
+      "python",
+      "-u",
+      "[DEPOT_TOOLS]/gn.py",
+      "--root=[SLAVE_BUILD]/pdfium",
+      "gen",
+      "//out/Release",
+      "--args=is_debug=false pdf_enable_v8=true pdf_enable_xfa=true pdf_use_skia=false pdf_is_standalone=true"
+    ],
+    "cwd": "[SLAVE_BUILD]/pdfium",
+    "name": "gn gen"
+  },
+  {
+    "cmd": [
       "ninja",
       "-C",
       "[SLAVE_BUILD]/pdfium/out/Release"
@@ -120,4 +134,4 @@
     "recipe_result": null,
     "status_code": 0
   }
-]
+]