[fuchsia] Add QEMU third_party download dep entry to v8 DEPS.

The Fuchsia SDK will no longer include QEMU as part of the tarball.
QEMU will be downloaded separately from CIPD instead.

Fixes V8 roll failure: https://chromium-review.googlesource.com/1180602

Tested by verifying that
//build/config/fuchsia:blobstore_extended_qcow2 builds using the updated
Chromium build targets in //build/fuchsia/.

Change-Id: I01795aaf45dcdaa1a05481e4a72302c7aa387b3a
Reviewed-on: https://chromium-review.googlesource.com/1181688
Commit-Queue: Kevin Marshall <kmarshall@chromium.org>
Reviewed-by: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55235}

DEPS

@@ -64,6 +64,16 @@ deps = {
     Var('chromium_url') + '/external/github.com/tc39/test262.git' + '@' + 'a6c1d05ac4fed084fa047e4c52ab2a8c9c2a8aef',
   'v8/test/test262/harness':
     Var('chromium_url') + '/external/github.com/test262-utils/test262-harness-py.git' + '@' + '0f2acdd882c84cff43b9d60df7574a1901e2cdcd',
+  'v8/third_party/qemu': {
+      'packages': [
+          {
+              'package': 'fuchsia/qemu/linux-amd64',
+              'version': '9cc486c5b18a0be515c39a280ca9a309c54cf994'
+          },
+      ],
+      'condition': 'checkout_fuchsia',
+      'dep_type': 'cipd',
+  },
   'v8/tools/clang':
     Var('chromium_url') + '/chromium/src/tools/clang.git' + '@' + '45de59deadbf80e96345cf94baf687c722185f80',
   'v8/tools/luci-go':