Run install-sysroot script before 'gn gen' on PDFium bot

infra/bots/recipes/swarm_compile.expected/Build-Ubuntu-GCC-x86_64-Release-PDFium.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "\nimport sys, os\npath = sys.argv[1]\nmode = int(sys.argv[2])\nif not os.path.isdir(path):\n  if os.path.exists(path):\n    print \"%s exists but is not a dir\" % path\n    sys.exit(1)\n  os.makedirs(path, mode)\n",
       "[CUSTOM_/_B_WORK]",
       "511"
     ],
     "name": "makedirs checkout_path",
@@ skipping 79 matching lines @@
       "BUILDTYPE": "Release",
       "CHROME_HEADLESS": "1",
       "GYP_DEFINES": "skia_arch_type=x86_64 skia_warnings_as_errors=1",
       "PATH": "%(PATH)s:RECIPE_PACKAGE_REPO[depot_tools]:RECIPE_PACKAGE_REPO[depot_tools]",
       "SKIA_OUT": "[CUSTOM_/_B_WORK]/skia/out/Build-Ubuntu-GCC-x86_64-Release-PDFium"
     },
     "name": "runhook"
   },
   {
     "cmd": [
+      "python",
+      "build/linux/sysroot_scripts/install-sysroot.py",
+      "--arch=amd64"
+    ],
+    "cwd": "[CUSTOM_/_B_WORK]/pdfium",
+    "env": {
+      "BUILDTYPE": "Release",
+      "CHROME_HEADLESS": "1",
+      "PATH": "%(PATH)s:RECIPE_PACKAGE_REPO[depot_tools]:RECIPE_PACKAGE_REPO[depot_tools]",
+      "SKIA_OUT": "[CUSTOM_/_B_WORK]/skia/out/Build-Ubuntu-GCC-x86_64-Release-PDFium"
+    },
+    "name": "sysroot"
+  },
+  {
+    "cmd": [
       "gn",
       "gen",
       "out/skia",
       "--args=pdf_use_skia=true pdf_is_standalone=true clang_use_chrome_plugins=false is_component_build=false is_debug=false"
     ],
     "cwd": "[CUSTOM_/_B_WORK]/pdfium",
     "env": {
       "BUILDTYPE": "Release",
       "CHROME_HEADLESS": "1",
       "CHROMIUM_BUILDTOOLS_PATH": "[CUSTOM_/_B_WORK]/pdfium/buildtools",
@@ skipping 91 matching lines @@
       "@@@STEP_LOG_LINE@python.inline@    shutil.move(f, dst_path)@@@",
       "@@@STEP_LOG_END@python.inline@@@"
     ]
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]