Reland Enable hermetic builds for iOS.

build/mac/should_use_hermetic_xcode.py

Index: build/mac/should_use_hermetic_xcode.py
diff --git a/build/mac/should_use_hermetic_xcode.py b/build/mac/should_use_hermetic_xcode.py
index 14ddfacdc5020b780334eb838ebe9bfddbd06314..68e288e32f7c05f670238b0aaec893cb93a996e3 100755
--- a/build/mac/should_use_hermetic_xcode.py
+++ b/build/mac/should_use_hermetic_xcode.py
@@ -4,7 +4,11 @@
 # found in the LICENSE file.
 
 """Prints "1" if Chrome targets should be built with hermetic xcode. Otherwise
-prints "0"."""
+prints "0".
+
+Usage:
+  python should_use_hermetic_xcode.py <target_os>
+"""
 
 import os
 import sys
@@ -15,7 +19,8 @@ def _IsCorpMachine():
 
 
 def main():
-  if os.environ.get('FORCE_MAC_TOOLCHAIN') or _IsCorpMachine():
+  allow_corp = sys.argv[1] == 'mac' and _IsCorpMachine()
+  if os.environ.get('FORCE_MAC_TOOLCHAIN') or allow_corp:
     return "1"
   else:
     return "0"