Some final cleanups leading up to The Official Switch to Gyp
see http://codereview.appspot.com/4580043

1. Create a single public skia.gyp file that all outside projects (Chrome,
Android, etc.) should depend on from now on.  I haven't yet created targets
suitable for those projects to use, but this is where we should add them.
2. Make gyp generate its Makefiles within out/ directory, rather than polluting
directories under source control.
3. Modify trunk/Makefile to automatically run gyp_skia and then call the
generated Makefile, to ease developer transition.



git-svn-id: http://skia.googlecode.com/svn/trunk@1526 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/gyp_skia b/gyp_skia
new file mode 100755
index 0000000..6a28773
--- /dev/null
+++ b/gyp_skia
@@ -0,0 +1,90 @@
+#!/usr/bin/python
+#
+# Copyright (C) 2011 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# This script is a wrapper which invokes gyp with the correct --depth argument,
+# and supports the automatic regeneration of build files if all.gyp is
+# changed (Linux-only).
+
+import glob
+import os
+import shlex
+import sys
+
+script_dir = os.path.dirname(__file__)
+
+# Directory within which we can find the gyp source.
+gyp_source_dir = os.path.join(script_dir, 'third_party', 'externals', 'gyp')
+
+# Directory within which we can find most of Skia's gyp configuration files.
+gyp_config_dir = os.path.join(script_dir, 'gyp')
+
+# Directory within which we want all generated files (including Makefiles)
+# to be written.
+output_dir = os.path.join(os.path.abspath(script_dir), 'out')
+
+sys.path.append(os.path.join(gyp_source_dir, 'pylib'))
+import gyp
+
+def additional_include_files(args=[]):
+  # Determine the include files specified on the command line.
+  # This doesn't cover all the different option formats you can use,
+  # but it's mainly intended to avoid duplicating flags on the automatic
+  # makefile regeneration which only uses this format.
+  specified_includes = set()
+  for arg in args:
+    if arg.startswith('-I') and len(arg) > 2:
+      specified_includes.add(os.path.realpath(arg[2:]))
+
+  result = []
+  def AddInclude(path):
+    if os.path.realpath(path) not in specified_includes:
+      result.append(path)
+
+  # Always include common.gypi
+  AddInclude(os.path.join(gyp_config_dir, 'common.gypi'))
+
+  return result
+
+if __name__ == '__main__':
+  args = sys.argv[1:]
+
+  # This could give false positives since it doesn't actually do real option
+  # parsing.  Oh well.
+  gyp_file_specified = False
+  for arg in args:
+    if arg.endswith('.gyp'):
+      gyp_file_specified = True
+      break
+
+  # If we didn't get a file, then fall back to assuming 'skia.gyp' from the
+  # same directory as the script.
+  if not gyp_file_specified:
+    args.append(os.path.join(script_dir, 'skia.gyp'))
+
+  args.extend(['-I' + i for i in additional_include_files(args)])
+  args.extend(['--depth', '.'])
+
+  # Tell gyp to write the Makefiles into output_dir
+  args.extend(['--generator-output', os.path.abspath(output_dir)])
+
+  # Tell make to write its output into the same dir
+  args.extend(['-Goutput_dir=.'])
+
+  print 'Updating projects from gyp files...'
+  sys.stdout.flush()
+
+  # Off we go...
+  sys.exit(gyp.main(args))