pw_presubmit: gn check system and generated files

- In presubmit, do gn check in a separate step and specify
  --check-generated and --check-system.
- Fix gn check issues in pw_fuzzer by adding a missing dependency.
- Disable include checking for generated pw_rpc headers since they
  include internal pw_rpc headers.

Change-Id: I8b9f03957ac60166eeb141bcba9dc493bfc6350c
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/44562
Pigweed-Auto-Submit: Wyatt Hepler <hepler@google.com>
Reviewed-by: Armando Montanez <amontanez@google.com>
Commit-Queue: Wyatt Hepler <hepler@google.com>
diff --git a/pw_fuzzer/BUILD.gn b/pw_fuzzer/BUILD.gn
index e97d084..1359db4 100644
--- a/pw_fuzzer/BUILD.gn
+++ b/pw_fuzzer/BUILD.gn
@@ -19,8 +19,9 @@
 import("$dir_pw_fuzzer/fuzzer.gni")
 import("$dir_pw_fuzzer/oss_fuzz.gni")
 
-config("default_config") {
+config("public_include_path") {
   include_dirs = [ "public" ]
+  visibility = [ ":*" ]
 }
 
 # This is added automatically by the `pw_fuzzer` template.
@@ -45,7 +46,7 @@
 }
 
 pw_source_set("pw_fuzzer") {
-  public_configs = [ ":default_config" ]
+  public_configs = [ ":public_include_path" ]
   public = [
     "public/pw_fuzzer/asan_interface.h",
     "public/pw_fuzzer/fuzzed_data_provider.h",
@@ -54,7 +55,7 @@
 }
 
 pw_source_set("run_as_unit_test") {
-  configs = [ ":default_config" ]
+  configs = [ ":public_include_path" ]
   sources = [ "pw_fuzzer_disabled.cc" ]
   deps = [
     dir_pw_log,