Simplify //mojo/public/c/system targets

sky/engine/platform/BUILD.gn

Index: sky/engine/platform/BUILD.gn
diff --git a/sky/engine/platform/BUILD.gn b/sky/engine/platform/BUILD.gn
index 8b1f5e1b24b90587462eebbc55e584a67a03a509..e43e4fff9c2718d8f191edffec9e003f66344e52 100644
--- a/sky/engine/platform/BUILD.gn
+++ b/sky/engine/platform/BUILD.gn
@@ -84,11 +84,9 @@ group("make_platform_generated") {
   ]
 }
 
-component("platform") {
+source_set("platform") {
   visibility += [ "//sky/*" ]
 
-  output_name = "sky_platform"
-
   sources = [
     "animation/AnimationUtilities.h",
     "animation/AnimationValue.h",
@@ -644,7 +642,7 @@ component("platform") {
     "//mojo/application",
     "//mojo/common",
     "//mojo/environment:chromium",
-    "//mojo/public/c/system:for_shared_library",
+    "//mojo/public/c/system",
     "//mojo/public/cpp/bindings",
     "//mojo/public/cpp/system",
     "//mojo/public/cpp/utility",
@@ -756,6 +754,12 @@ test("platform_unittests") {
     "//url",
   ]
 
+  # TODO(abarth): This is a lie - this test is not embedded in an environment
+  # that injects the system thunks, so system calls don't actually work. This
+  # just tricks the linker into thinking that an implementation of these calls
+  # will be injected at runtime so the link succeeds.
+  deps += [ "//mojo/public/platform/native:system" ]
+
   defines = [ "INSIDE_BLINK" ]
 
   include_dirs = [ "$root_build_dir" ]