Port chromium landmines script.

build/landmine_utils.py

Index: build/landmine_utils.py
diff --git a/build/landmine_utils.py b/build/landmine_utils.py
index e8b7c98d5fc6a38104854ae3c0c48c543d92d91a..cb3499132a3c2f0b434eee1fadd6bdc513541db7 100644
--- a/build/landmine_utils.py
+++ b/build/landmine_utils.py
@@ -47,10 +47,19 @@ def gyp_defines():
   return dict(arg.split('=', 1)
       for arg in shlex.split(os.environ.get('GYP_DEFINES', '')))
 
+
+@memoize()
+def gyp_generator_flags():
+  """Parses and returns GYP_GENERATOR_FLAGS env var as a dictionary."""
+  return dict(arg.split('=', 1)
+      for arg in shlex.split(os.environ.get('GYP_GENERATOR_FLAGS', '')))
+
+
 @memoize()
 def gyp_msvs_version():
   return os.environ.get('GYP_MSVS_VERSION', '')
 
+
 @memoize()
 def distributor():
   """