[Swarming] Add missing files to gcmole isolate.

BUG=chromium:535160
LOG=n
TBR=tandrii@chromium.org, kjellander@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/1706783002

Cr-Commit-Position: refs/heads/master@{#34079}

tools/gcmole/run-gcmole.isolate

@@ -13,9 +13,11 @@
       'run-gcmole.py',
       # The following contains all relevant source and gyp files.
       '../gyp/v8.gyp',
+      '../../base/',
       '../../include/',
       '../../src/',
       '../../test/cctest/',
+      '../../third_party/icu/source/',
     ],
   },
   'conditions': [