Simplify //mojo/public/c/system targets

mojo/public/python/BUILD.gn

Index: mojo/public/python/BUILD.gn
diff --git a/mojo/public/python/BUILD.gn b/mojo/public/python/BUILD.gn
index 70402e778102c6f4a14a68ae89df8f1feff996a2..4058758ca576b822f68438420ec1f3d5d193e481 100644
--- a/mojo/public/python/BUILD.gn
+++ b/mojo/public/python/BUILD.gn
@@ -23,11 +23,12 @@ python_binary_module("system") {
   deps = [
     ":base",
     "../c/environment",
-    "../c/system:for_shared_library",
+    "../c/system",
     "../cpp/environment:standalone",
     "../cpp/system",
     "../cpp/utility",
     "../cpp/bindings:callback",
+    "../platform/native:system",
   ]
 }
 
@@ -45,11 +46,12 @@ python_binary_module("system_impl") {
   deps = [
     ":base",
     "../c/environment",
-    "../c/system:for_shared_library",
+    "../c/system",
     "../cpp/environment:standalone",
     "../cpp/system",
     "../cpp/utility",
     "../cpp/bindings:callback",
+    "../platform/native:system",
   ]
 }