[cpp] Demote public config to local cflags

Don't propagate warning suppressions to dependents.

Change-Id: I6e5b3fad006b40af9d37c5edb2a87689bf6130ea
Reviewed-on: https://fuchsia-review.googlesource.com/c/third_party/processor-trace/+/600891
Reviewed-by: Tamir Duberstein <tamird@google.com>
diff --git a/libipt/BUILD.gn b/libipt/BUILD.gn
index e5f2dc2..0417950 100644
--- a/libipt/BUILD.gn
+++ b/libipt/BUILD.gn
@@ -2,15 +2,6 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-config("libipt_config") {
-  # Suppress warnings in upstream code that are triggered by Fuchsia compilation flags.
-  cflags = [
-    "-Wno-conversion",
-    "-Wno-implicit-fallthrough",
-  ]
-  visibility = [ ":*" ]
-}
-
 static_library("libipt") {
   sources = [
     "include/intel-pt.h",
@@ -105,7 +96,10 @@
     "INCLUDE_EARLY_INIT",
   ]
 
-  public_configs = [ ":libipt_config" ]
-
-  cflags = [ "-Wno-strict-prototypes" ]
+  # Suppress warnings in upstream code that are triggered by Fuchsia compilation flags.
+  cflags = [
+    "-Wno-conversion",
+    "-Wno-implicit-fallthrough",
+    "-Wno-strict-prototypes",
+  ]
 }