pw_multisink: Add module config argument

No-Docs-Update-Reason: Update BUILD.gn structure, no functional changes.
Change-Id: I837d521eb5316aec1b675181cb1088f7b1bb8bc6
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/49761
Commit-Queue: Prashanth Swaminathan <prashanthsw@google.com>
Reviewed-by: Armando Montanez <amontanez@google.com>

pw_multisink/BUILD.gn

diff --git a/pw_multisink/BUILD.gn b/pw_multisink/BUILD.gn
index 20d5c24..2e8ea3f 100644
--- a/pw_multisink/BUILD.gn
+++ b/pw_multisink/BUILD.gn
@@ -14,22 +14,34 @@
 
 import("//build_overrides/pigweed.gni")
 
+import("$dir_pw_build/module_config.gni")
 import("$dir_pw_build/target_types.gni")
 import("$dir_pw_docgen/docs.gni")
 import("$dir_pw_unit_test/test.gni")
 
-config("default_config") {
+declare_args() {
+  # The build target that overrides the default configuration options for this
+  # module. This should point to a source set that provides defines through a
+  # public config (which may -include a file or add defines directly).
+  pw_multisink_CONFIG = pw_build_DEFAULT_MODULE_CONFIG
+}
+
+config("public_include_path") {
   include_dirs = [ "public" ]
   visibility = [ ":*" ]
 }
 
+pw_source_set("config") {
+  public = [ "public/pw_multisink/config.h" ]
+  public_configs = [ ":public_include_path" ]
+  public_deps = [ pw_multisink_CONFIG ]
+}
+
 pw_source_set("pw_multisink") {
-  public_configs = [ ":default_config" ]
-  public = [
-    "public/pw_multisink/config.h",
-    "public/pw_multisink/multisink.h",
-  ]
+  public_configs = [ ":public_include_path" ]
+  public = [ "public/pw_multisink/multisink.h" ]
   public_deps = [
+    ":config",
     "$dir_pw_bytes",
     "$dir_pw_containers",
     "$dir_pw_result",