[fuchsia] Use original executable filename instead of /pkg/bin/app.

The Fuchsia component manifest now allows us to specify arbitrary
binaries in a package as an entry point. Before, the entry point
executable had to reside at the special path /pkg/bin/app.

Keeping the executable name intact will facilitate stack trace
symbolization on multiple packages.

Bug: 798851

Change-Id: Ib116602e2e0e430478d24829112df63c27f3d025
Reviewed-on: https://chromium-review.googlesource.com/1208716
Commit-Queue: Kevin Marshall <kmarshall@chromium.org>
Reviewed-by: Kevin Marshall <kmarshall@chromium.org>
Reviewed-by: Wez <wez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#589283}

build/config/fuchsia/build_manifest.py

@@ -197,7 +197,6 @@ def BuildManifest(root_dir, out_dir, app_name, app_filename,
       in_package_path = MakePackagePath(os.path.join(out_dir, current_file),
                                         [gen_dir, root_dir, out_dir])
       if in_package_path == app_filename:
-        in_package_path = 'bin/app'
         app_found = True
 
       # The source path is relativized so that it can be used on multiple
@@ -220,7 +219,7 @@ def BuildManifest(root_dir, out_dir, app_name, app_filename,
     with open(os.path.join(os.path.dirname(output_path),
                            app_name + '.cmx'), 'w') as component_manifest_file:
       component_manifest = {
-          'program': { 'binary': 'bin/app' },
+          'program': { 'binary': app_filename },
           'sandbox': json.load(open(sandbox_policy_path, 'r')),
       }
       json.dump(component_manifest, component_manifest_file)