Un-nest configs in GN files.

third_party/usrsctp/BUILD.gn

Index: third_party/usrsctp/BUILD.gn
diff --git a/third_party/usrsctp/BUILD.gn b/third_party/usrsctp/BUILD.gn
index bbea24b858fea7de37599c9a6345f7a2f7ea2763..3accc19e29f128ba06e60cac4cde6c4d33ea20c0 100644
--- a/third_party/usrsctp/BUILD.gn
+++ b/third_party/usrsctp/BUILD.gn
@@ -11,6 +11,13 @@ config("usrsctp_config") {
   ]
 }
 
+config("usrsctp_warnings") {
+  if (is_clang) {
+    # atomic_init in user_atomic.h is a static function in a header.
+    cflags = [ "-Wno-unused-function" ]
+  }
+}
+
 static_library("usrsctp") {
   sources = [
     "usrsctplib/netinet/sctp.h",
@@ -84,16 +91,12 @@ static_library("usrsctp") {
     # "SCTP_DEBUG", # Uncomment for SCTP debugging.
   ]
 
-  config("usrsctp_warnings") {
-    if (is_clang) {
-      # atomic_init in user_atomic.h is a static function in a header.
-      cflags = [ "-Wno-unused-function" ]
-    }
-  }
   configs -= [ "//build/config/compiler:chromium_code" ]
-  configs += [ "//build/config/compiler:no_chromium_code" ]
-  configs += [ "//build/config/compiler:no_incompatible_pointer_warnings" ]
-  configs += [ ":usrsctp_warnings" ]
+  configs += [
+    ":usrsctp_warnings",
+    "//build/config/compiler:no_chromium_code",
+    "//build/config/compiler:no_incompatible_pointer_warnings",
+  ]
 
   public_configs = [ ":usrsctp_config" ]