mac: Make it possible to download mac sdk on a linux host.

This is apparently used by ffmpeg's robosushi tool, when doing ffmpeg
rolls -- except they currently pull the SDK off a GCS bucket instead
of using cipd like Chromium normally does nowadays. This makes it
possible to make robosushi use the more common method.

Bug: 1098899
Change-Id: I0a2aea6cd0316e536bb3501801831817a5290def
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2277455
Auto-Submit: Nico Weber <thakis@chromium.org>
Reviewed-by: Erik Chen <erikchen@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#784530}

build/mac/should_use_hermetic_xcode.py

@@ -28,7 +28,15 @@ import mac_toolchain
 
 
 def _IsCorpMachine():
-  return os.path.isdir('/Library/GoogleCorpSupport/')
+  if sys.platform == 'darwin':
+    return os.path.isdir('/Library/GoogleCorpSupport/')
+  if sys.platform.startswith('linux'):
+    import subprocess
+    try:
+      return subprocess.check_output('lsb_release -sc').rstrip() == 'rodete'
+    except:
+      return False
+  return False
 
 
 def main():

build/mac_toolchain.py

@@ -60,6 +60,8 @@ PARANOID_MODE = '$ParanoidMode CheckIntegrity\n'
 
 
 def PlatformMeetsHermeticXcodeRequirements(version):
+  if sys.platform != 'darwin':
+    return True
   needed = MAC_MINIMUM_OS_VERSION[version]
   major_version = map(int, platform.release().split('.')[:len(needed)])
   return major_version >= needed
@@ -130,6 +132,9 @@ def InstallXcodeBinaries(version, binaries_root=None):
     RequestCipdAuthentication()
     return 1
 
+  if sys.platform != 'darwin':
+    return 0
+
   # Accept the license for this version of Xcode if it's newer than the
   # currently accepted version.
   cipd_xcode_version_plist_path = os.path.join(
@@ -178,9 +183,6 @@ def InstallXcodeBinaries(version, binaries_root=None):
 
 
 def main():
-  if sys.platform != 'darwin':
-    return 0
-
   if not _UseHermeticToolchain():
     print('Skipping Mac toolchain installation for mac')
     return 0