Add support for GYP_GENERATOR_FLAGS out dir setting for landmines

BUG=421894

Review URL: https://codereview.chromium.org/695753002

Cr-Commit-Position: refs/heads/master@{#302419}


CrOS-Libchrome-Original-Commit: 6bad0d4fad0ee39e993d90eb2ab8050d650efa2b
diff --git a/build/landmine_utils.py b/build/landmine_utils.py
index 7737832..9b667d0 100644
--- a/build/landmine_utils.py
+++ b/build/landmine_utils.py
@@ -48,6 +48,12 @@
       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', '')