EDK: Split the mojo_edk_system_unittests target.

mojo/BUILD.gn

Index: mojo/BUILD.gn
diff --git a/mojo/BUILD.gn b/mojo/BUILD.gn
index c268b52b90e91ff70536e372628e4ea2f8e79d62..eecb107bce4e543d2804a116717a9034330c9a92 100644
--- a/mojo/BUILD.gn
+++ b/mojo/BUILD.gn
@@ -63,15 +63,15 @@ group("tests") {
   deps = [
     ":public_tests",
     "//mojo/common:mojo_common_unittests",
-    "//mojo/edk/system:tests",
     "//mojo/dart/embedder/test:dart_unittests",
-    "//mojo/public/cpp/bindings/tests:versioning_apptests",
-    "//mojo/services/view_manager/cpp/tests:mojo_view_manager_lib_unittests",
-    "//mojo/tools:message_generator",
+    "//mojo/edk:tests",
     "//mojo/gles2:mgl_unittests",
     "//mojo/gpu:apptests",
+    "//mojo/public/cpp/bindings/tests:versioning_apptests",
     "//mojo/services/files/c:apptests",
     "//mojo/services/files/cpp:files_impl_apptests",
+    "//mojo/services/view_manager/cpp/tests:mojo_view_manager_lib_unittests",
+    "//mojo/tools:message_generator",
   ]
 
   if (is_linux || is_android) {