Split arm and arm64 android trybots work directories.

masters/master.tryserver.chromium.android/builders.pyl

 {
   "master_base_class": "Master4a",
   "master_port": 21401,
   "master_port_alt": 41401,
   "slave_port": 31401,
   "templates": ["templates", "../master.chromium/templates"],
 
   "service_account_file": "service-account-chromium-tryserver.json",
   "buildbucket_bucket": "master.tryserver.chromium.android",
 
@@ skipping 89 matching lines @@
       "slavebuilddir": "android",
       "slave_pools": ["slaves_with_devices"],
     },
     "linux_android_rel_ng": {
       "builder_timeout_s": 11400,  # 60 * 190
       "recipe": "chromium_trybot",
       "scheduler": None,
       "slavebuilddir": "android",
       "slave_pools": ["ccompute_android_launch"],
     },
-    "android_swarming_rel": {
-      "builder_timeout_s": 6900,  # 60 * 115
-      "recipe": "chromium_trybot",
-      "scheduler": None,
-      "slavebuilddir": "android",
-      "slave_pools": ["ccompute_android_launch"],
-    },
     "android_n5x_swarming_rel": {
       "builder_timeout_s": 6900,  # 60 * 115
       "recipe": "chromium_trybot",
       "scheduler": None,
-      "slavebuilddir": "android",
+      "slavebuilddir": "android_arm64",
       "slave_pools": ["ccompute_android_launch"],
     },
     "android_chromium_variable": {
       "builder_timeout_s": 36000,  # 60 * 600
       "recipe": "findit/chromium/compile",
       "scheduler": None,
       "slavebuilddir": "android",
       "slave_pools": ["ccompute_optional_bots"],
     },
     "android_chromium_variable_arm64": {
@@ skipping 314 matching lines @@
         "os": "linux",
         "version": "precise",
         "bits": 64,
       },
       "slaves": [
         "build35-b4",
       ],
     }
   }
 }