GN (android): Fix md5sum_bin_host not working for component builds

tools/android/md5sum/BUILD.gn

 # 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.
 
 # GYP: //tools/android/md5sum/md5sum.gyp:md5sum
 group("md5sum") {
   datadeps = [
-    ":md5sum_bin($host_toolchain)",
-    ":md5sum_bin($default_toolchain)",
     ":md5sum_prepare_dist($default_toolchain)",
     ":md5sum_copy_host($host_toolchain)",
   ]
 
   # TODO(cjhopman): Remove once group datadeps are fixed.
   deps = datadeps
 }
 
 # GYP: //tools/android/md5sum/md5sum.gyp:md5sum_bin_device (and md5sum_bin_host)
 executable("md5sum_bin") {
@@ skipping 18 matching lines @@
   # GYP: //tools/android/md5sum/md5sum.gyp:md5sum_stripped_device_bin
   create_native_executable_dist("md5sum_prepare_dist") {
     dist_dir = "$root_build_dir/md5sum_dist"
     binary = "$root_build_dir/exe.stripped/md5sum_bin"
     deps = [
       ":md5sum_bin",
     ]
   }
 } else {
   # GYP: //tools/android/md5sum/md5sum.gyp:md5sum_bin_host
-  copy("md5sum_copy_host") {
+  action("md5sum_copy_host") {
+    # Symlink rather than copy so that it still works for component builds

[brettw, 2015/07/15 17:31:28]

This doesn't say *why* we need to symlink for component builds, so I don't
understand the motivation for this change.

[agrieve, 2015/07/15 17:57:53]

Good point. Done.

+    script = "//build/symlink.py"
+    _src = "$root_out_dir/md5sum_bin"
+    _target = "$root_build_dir/md5sum_bin_host"
     sources = [
-      "$root_out_dir/md5sum_bin",
+      _src,
     ]
     outputs = [
-      "$root_build_dir/md5sum_bin_host",
+      _target,
     ]
     deps = [
       ":md5sum_bin",
     ]
+    args = [
+      "-f",
+      rebase_path(_src, root_build_dir),
+      rebase_path(_target, root_build_dir),
+    ]
   }
 }