EDK: Remove MOJO_SYSTEM_IMPL_EXPORT, system_impl_export.h, etc.

mojo/edk/embedder/BUILD.gn

Index: mojo/edk/embedder/BUILD.gn
diff --git a/mojo/edk/embedder/BUILD.gn b/mojo/edk/embedder/BUILD.gn
index b58c2935ee52dbe219e83a4dbb142ba780d857f4..fccf099837f1740f1811347177f008d01cbfa6d9 100644
--- a/mojo/edk/embedder/BUILD.gn
+++ b/mojo/edk/embedder/BUILD.gn
@@ -26,10 +26,7 @@ mojo_edk_source_set("embedder") {
     "test_embedder.h",
   ]
 
-  defines = [
-    "MOJO_SYSTEM_IMPL_IMPLEMENTATION",
-    "MOJO_SYSTEM_IMPLEMENTATION",
-  ]
+  defines = [ "MOJO_SYSTEM_IMPLEMENTATION" ]
 
   mojo_edk_configs = [ "mojo/edk/system:system_config" ]
 
@@ -81,8 +78,6 @@ mojo_edk_source_set("platform") {
     "simple_platform_support.h",
   ]
 
-  defines = [ "MOJO_SYSTEM_IMPL_IMPLEMENTATION" ]
-
   mojo_edk_configs = [ "mojo/edk/system:system_config" ]
 
   mojo_sdk_public_deps = [ "mojo/public/cpp/system" ]
@@ -113,8 +108,6 @@ mojo_edk_source_set("delegates") {
     "slave_process_delegate.h",
   ]
 
-  defines = [ "MOJO_SYSTEM_IMPL_IMPLEMENTATION" ]
-
   mojo_edk_configs = [ "mojo/edk/system:system_config" ]
 
   mojo_sdk_public_deps = [ "mojo/public/cpp/system" ]