Port chromium landmines script.

build/gyp_environment.py

Index: build/gyp_environment.py
diff --git a/build/gyp_environment.py b/build/gyp_environment.py
new file mode 100644
index 0000000000000000000000000000000000000000..f1cee6ef8e00f628dc54e319bc39fb6f4fb146f3
--- /dev/null
+++ b/build/gyp_environment.py
@@ -0,0 +1,52 @@
+# Copyright 2015 the V8 project authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""
+Sets up various automatic gyp environment variables. These are used by
+gyp_v8 and landmines.py which run at different stages of runhooks. To
+make sure settings are consistent between them, all setup should happen here.
+"""
+
+import os
+import sys
+
+SCRIPT_DIR = os.path.dirname(os.path.realpath(__file__))
+V8_ROOT = os.path.abspath(os.path.join(SCRIPT_DIR, os.pardir))
+
+
+def apply_gyp_environment(file_path=None):
+  """
+  Reads in a *.gyp_env file and applies the valid keys to os.environ.
+  """
+  if not file_path or not os.path.exists(file_path):
+    return
+  file_contents = open(file_path).read()
+  try:
+    file_data = eval(file_contents, {'__builtins__': None}, None)
+  except SyntaxError, e:
+    e.filename = os.path.abspath(file_path)
+    raise
+  supported_vars = ( 'V8_GYP_FILE',
+                     'V8_GYP_SYNTAX_CHECK',
+                     'GYP_DEFINES',
+                     'GYP_GENERATOR_FLAGS',
+                     'GYP_GENERATOR_OUTPUT', )
+  for var in supported_vars:
+    val = file_data.get(var)
+    if val:
+      if var in os.environ:
+        print 'INFO: Environment value for "%s" overrides value in %s.' % (
+            var, os.path.abspath(file_path)
+        )
+      else:
+        os.environ[var] = val
+
+
+def set_environment():
+  """Sets defaults for GYP_* variables."""
+
+  if 'SKIP_V8_GYP_ENV' not in os.environ:
+    # Update the environment based on v8.gyp_env
+    gyp_env_path = os.path.join(os.path.dirname(V8_ROOT), 'v8.gyp_env')
+    apply_gyp_environment(gyp_env_path)