build: document electron goma usage and add the external binaries (#21622)

script/external-binaries.json

@@ -43,6 +43,21 @@
       "url": "sccache-win32-x64.zip",
       "platform": "win32",
       "sha": "b6a20fd1c2026f3792e7286bc768a7ebc261847b76449b49f55455e1f841fecd"
+    },
+    {
+      "url": "goma-win.zip",
+      "platform": "win32",
+      "sha": "f97c88aa5d49395ae20387b6329ad406fd019f5fb4aac4ba639ca928b7151f6b"
+    },
+    {
+      "url": "goma-linux.tgz",
+      "platform": "linux",
+      "sha": "1cb3099a40f6200ae57216efa26af795c587b6ac7ae97955d1078d0b1e3011a6"
+    },
+    {
+      "url": "goma-mac.tgz",
+      "platform": "darwin",
+      "sha": "da1e7de82fbf3b99f1a9d0f9bf51b25e75e8778fec180deb72cff873813d717c"
     }
   ]
 }

script/update-external-binaries.py

@@ -5,6 +5,7 @@ import errno
 import hashlib
 import json
 import os
+import tarfile
 
 from lib.config import PLATFORM, get_target_arch
 from lib.util import add_exec_bit, download, extract_zip, rm_rf, \
@@ -51,8 +52,12 @@ def main():
 
     temp_path = download_binary(base_url, version, binary['url'], binary['sha'])
 
-    # We assume that all binaries are in zip archives.
-    extract_zip(temp_path, output_dir)
+    if temp_path.endswith('.zip'):
+      extract_zip(temp_path, output_dir)
+    else:
+      tar = tarfile.open(temp_path, "r:gz")
+      tar.extractall(output_dir)
+      tar.close()
 
     # Hack alert. Set exec bit for sccache binaries.
     # https://bugs.python.org/issue15795