Switch all buildbots to GN build

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

 [
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_MODULE[depot_tools::bot_update]\\resources\\bot_update.py",
       "--master",
       "client.pdfium",
       "--builder",
-      "windows_xfa_64_rel",
+      "windows_xfa_rel_gyp",
       "--slave",
       "test_slave",
       "--spec",
       "cache_dir = '[GIT_CACHE]'\nsolutions = [{'deps_file': 'DEPS', 'managed': True, 'name': 'pdfium', 'url': 'https://pdfium.googlesource.com/pdfium.git'}]",
       "--root",
       "pdfium",
       "--revision_mapping_file",
       "{}",
       "--git-cache-dir",
       "[GIT_CACHE]",
@@ skipping 36 matching lines @@
     "env": {
       "GYP_DEFINES": "pdf_enable_v8=1 pdf_enable_xfa=1 target_arch=x64",
       "PATH": "%(PATH)s;RECIPE_PACKAGE_REPO[depot_tools]"
     },
     "name": "gclient runhooks"
   },
   {
     "cmd": [
       "ninja",
       "-C",
-      "[SLAVE_BUILD]\\pdfium\\out\\Release_x64"
+      "[SLAVE_BUILD]\\pdfium\\out\\Release"
     ],
     "name": "compile with ninja"
   },
   {
     "cmd": [
-      "[SLAVE_BUILD]\\pdfium\\out\\Release_x64\\pdfium_unittests.exe"
+      "[SLAVE_BUILD]\\pdfium\\out\\Release\\pdfium_unittests.exe"
     ],
     "cwd": "[SLAVE_BUILD]\\pdfium",
     "name": "unittests"
   },
   {
     "cmd": [
-      "[SLAVE_BUILD]\\pdfium\\out\\Release_x64\\pdfium_embeddertests.exe"
+      "[SLAVE_BUILD]\\pdfium\\out\\Release\\pdfium_embeddertests.exe"
     ],
     "cwd": "[SLAVE_BUILD]\\pdfium",
     "name": "embeddertests"
   },
   {
     "cmd": [
       "python",
       "-u",
       "[SLAVE_BUILD]\\pdfium\\testing\\tools\\run_javascript_tests.py",
       "--build-dir",
-      "out\\Release_x64"
+      "out\\Release"
     ],
     "cwd": "[SLAVE_BUILD]\\pdfium",
     "name": "javascript tests"
   },
   {
     "cmd": [
       "python",
       "-u",
       "[SLAVE_BUILD]\\pdfium\\testing\\tools\\run_pixel_tests.py",
       "--build-dir",
-      "out\\Release_x64"
+      "out\\Release"
     ],
     "cwd": "[SLAVE_BUILD]\\pdfium",
     "name": "pixel tests"
   },
   {
     "cmd": [
       "python",
       "-u",
       "[SLAVE_BUILD]\\pdfium\\testing\\tools\\run_corpus_tests.py",
       "--build-dir",
-      "out\\Release_x64"
+      "out\\Release"
     ],
     "cwd": "[SLAVE_BUILD]\\pdfium",
     "name": "corpus tests"
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
-]
+]