Add a snapshot of flutter/engine/src/build to our sdk

build/gyp_environment.py

Index: build/gyp_environment.py
diff --git a/build/gyp_environment.py b/build/gyp_environment.py
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index 0000000000000000000000000000000000000000..fb50645d56fc5adc4276f9ac989a06059c4c4aa3
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+++ b/build/gyp_environment.py
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+# Copyright 2014 The Chromium 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_chromium and landmines.py which run at different stages of runhooks. To
+make sure settings are consistent between them, all setup should happen here.
+"""
+
+import gyp_helper
+import os
+import sys
+import vs_toolchain
+
+def SetEnvironment():
+  """Sets defaults for GYP_* variables."""
+  gyp_helper.apply_chromium_gyp_env()
+
+  # Default to ninja on linux and windows, but only if no generator has
+  # explicitly been set.
+  # Also default to ninja on mac, but only when not building chrome/ios.
+  # . -f / --format has precedence over the env var, no need to check for it
+  # . set the env var only if it hasn't been set yet
+  # . chromium.gyp_env has been applied to os.environ at this point already
+  if sys.platform.startswith(('linux', 'win', 'freebsd')) and \
+      not os.environ.get('GYP_GENERATORS'):
+    os.environ['GYP_GENERATORS'] = 'ninja'
+  elif sys.platform == 'darwin' and not os.environ.get('GYP_GENERATORS') and \
+      not 'OS=ios' in os.environ.get('GYP_DEFINES', []):
+    os.environ['GYP_GENERATORS'] = 'ninja'
+
+  vs_toolchain.SetEnvironmentAndGetRuntimeDllDirs()