Checkpoint work to get GN builds working on Android.

build/config/android/BUILD.gn

+# Copyright 2013 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.
+
+import("//build/config/android/config.gni")
+import("//build/config/sysroot.gni")
+
+config("sdk") {
+  if (sysroot != "") {
+    cflags = [ "--sysroot=" + sysroot ]
+    ldflags = [ "--sysroot=" + sysroot ]
+
+    # Need to get some linker flags out of the sysroot.
+    sysroot_ld_path = rebase_path("//build/config/linux/sysroot_ld_path.py")
+    ldflags += [ exec_script(sysroot_ld_path,
+        [ rebase_path("//build/linux/sysroot_ld_path.sh"), sysroot ],
+        "value")
+    ]

[Dirk Pranke, 2014/04/08 00:39:22]

Is this the right way to say "exec_script(<path-to-script>)" if script is not
next to the BUILD.gn file?

[brettw, 2014/04/09 05:37:08]

Yes, although we shouldn't be running this script in multiple places (the linux
build file also calls this). In this case we should put it in the .gni file so
it only gets forked once.

[Dirk Pranke, 2014/04/09 18:49:20]

I don't think I understand this comment, possibly because I don't fully
understand GN's execution model yet to understand what things get executed more
than once vs. just once. 

However, since this file gets conditionally pulled in from BUILDCONFIG.gn, don't
we only get one or the other? Also, since linux and android will have different
sysroots, wouldn't we *have* to call this twice?

[brettw, 2014/04/09 20:33:19]

I guess you're right we'll only get one or the other. So this is fine.

+  }
+}