[Fuchsia] Add check for sdk update

Due to the transition to CIPD, sometimes the SDK directory will end up
in a bad state on builders, where only the .hash file remains. Adds a
check so that in scenarios like this, the SDK is still downloaded.

Bug: 1325179
Change-Id: I5e0bb912dfca46c6aeec677ae449fc41179f0c42
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3653415
Commit-Queue: Chong Gu <chonggu@google.com>
Reviewed-by: Sergey Ulanov <sergeyu@chromium.org>
Auto-Submit: Chong Gu <chonggu@google.com>
Cr-Commit-Position: refs/heads/main@{#1004868}

build/fuchsia/update_sdk.py

@@ -21,6 +21,7 @@ from common import GetHostOsFromPlatform, GetHostArchFromPlatform, \
 sys.path.append(os.path.join(DIR_SOURCE_ROOT, 'build'))
 import find_depot_tools
 
+LICENSE_FILE = 'LICENSE'
 SDK_SIGNATURE_FILE = '.hash'
 SDK_TARBALL_PATH_TEMPLATE = (
     'gs://{bucket}/development/{sdk_hash}/sdk/{platform}-amd64/gn.tar.gz')
@@ -154,9 +155,14 @@ def main():
     return 1
 
   signature_filename = os.path.join(SDK_ROOT, SDK_SIGNATURE_FILE)
+
+  # crbug.com/1325179: Need to check LICENSE file existence due to transition
+  # to using CIPD to download the SDK.
+  license_filename = os.path.join(SDK_ROOT, LICENSE_FILE)
+
   current_signature = (open(signature_filename, 'r').read().strip()
                        if os.path.exists(signature_filename) else '')
-  if current_signature != sdk_hash:
+  if current_signature != sdk_hash or not os.path.exists(license_filename):
     logging.info('Downloading GN SDK %s...' % sdk_hash)
 
     MakeCleanDirectory(SDK_ROOT)