Include mojo_main_{chromium,standalone}.cc instead of using a target

mojo/mojo_public.gypi

Index: mojo/mojo_public.gypi
diff --git a/mojo/mojo_public.gypi b/mojo/mojo_public.gypi
index 1d873fc4641bba5d3ffdc9fd4b8aa00c3f1dbdfe..ec9622f7960b28daa656831daa2793f20f4645da 100644
--- a/mojo/mojo_public.gypi
+++ b/mojo/mojo_public.gypi
@@ -382,32 +382,6 @@
         'mojo_service_provider_bindings',
       ],
     },
-    {
-      'target_name': 'mojo_main_standalone',
-      'type': 'static_library',
-      'sources': [
-        'public/cpp/application/lib/mojo_main_standalone.cc',
-      ],
-      'dependencies': [
-        'mojo_application',
-      ],
-      'export_dependent_settings': [
-        'mojo_application',
-      ],
-    },
-    {
-      'target_name': 'mojo_main_chromium',
-      'type': 'static_library',
-      'sources': [
-        'public/cpp/application/lib/mojo_main_chromium.cc',
-      ],
-      'dependencies': [
-        'mojo_application',
-      ],
-      'export_dependent_settings': [
-        'mojo_application',
-      ],
-    },
   ],
   'conditions': [
     ['OS == "android"', {
@@ -434,4 +408,8 @@
       ],
     }],
   ],
+  'variables': {
+    'mojo_main_standalone': "public/cpp/application/lib/mojo_main_standalone.cc",
+    'mojo_main_chromium': "public/cpp/application/lib/mojo_main_chromium.cc",
+  },
 }