[system-ota-tests] Update docs on how to run tests

The documentation detailing how to run the system ota tests locally
drifted out of sync with the current build system. This modernizes
the setup information. Furthermore, it describes how to authenticate
against luci in order to download the build artifacts.

Change-Id: I1f4bdf9dc4ad7f1d7852a44d63313e52f1c1970f
diff --git a/garnet/tests/system_ota_tests/README.md b/garnet/tests/system_ota_tests/README.md
index 1a8c5be..a965fb2 100644
--- a/garnet/tests/system_ota_tests/README.md
+++ b/garnet/tests/system_ota_tests/README.md
@@ -12,25 +12,35 @@
 into the system image. You can do this by running:
 
 ```
-% fx set x64 \
-  --product garnet/products/default.gni \
-  --available garnet/packages/tests/system_ota \
+% fx set core.x64 \
+  --with-base //third_party/sbase:cat \
+  --with-base //third_party/sbase:ls \
+  --with //garnet/tests/system_ota_tests \
   --args 'extra_authorized_keys_file="//.ssh/authorized_keys"'
 % fx build
 ```
 
-Finally, you can run the test with:
+Next, you need to authenticate against luci to be able to download build
+artifacts. Install chromium's `depot_tools` by following
+[these instructions](https://commondatastorage.googleapis.com/chrome-infra-docs/flat/depot_tools/docs/html/depot_tools_tutorial.html).
+Then, login to luci by running:
 
 ```
-% ~/fuchsia/out/x64/tools/system_ota_test \
-  -fuchsia-build-dir ~/fuchsia/out/x64 \
-  -zircon-tools-dir ~/fuchsia/out/build-zircon/tools \
-  -builder-name fuchsia/ci/fuchsia-x64-release \
-  upgrade
+% cd depot_tools
+% ./luci-auth login
+...
+```
+
+Now, you should be able to run the tests with:
+
+```
+~/fuchsia/out/default/host_x64/system_ota_tests_upgrade \
+  -ssh-private-key ~/fuchsia/.ssh/pkey \
+  -builder-name fuchsia/ci/fuchsia-x64-release
 ```
 
 This will run through the whole test. There are more options to the test, to see
-them all run `~/fuchsia/out/x64/tools/system_ota_test -- -h`.
+them all run `~/fuchsia/out/default/host_x64/system_ota_tests_upgrade -- -h`.
 
 ## Running the tests locally in QEMU
 
@@ -73,9 +83,10 @@
 output to the terminal:
 
 ```
-% fx set x64 \
-  --product garnet/products/default.gni \
-  --available garnet/packages/tests/system_ota \
+% fx set core.x64 \
+  --with-base //third_party/sbase:cat \
+  --with-base //third_party/sbase:ls \
+  --with //garnet/tests/system_ota_tests \
   --args 'extra_authorized_keys_file="//.ssh/authorized_keys"' \
   --args 'kernel_cmdline_args=["kernel.serial=legacy"]'
 % fx build