misc: source_set -> pw_source_set

This updates several uses of GN's builtin source_set to use
pw_source_set instead.

Change-Id: I067ad500016db7b96ba9ec5a057680639e6c6f73
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/17640
Reviewed-by: Armando Montanez <amontanez@google.com>
Reviewed-by: Ewout van Bekkum <ewout@google.com>
Commit-Queue: Alexei Frolov <frolv@google.com>
diff --git a/pw_fuzzer/BUILD.gn b/pw_fuzzer/BUILD.gn
index 130a05b..bacee77 100644
--- a/pw_fuzzer/BUILD.gn
+++ b/pw_fuzzer/BUILD.gn
@@ -76,7 +76,7 @@
   public_deps = [ "$dir_pw_log" ]
 }
 
-source_set("run_as_unit_test") {
+pw_source_set("run_as_unit_test") {
   configs = [ ":default_config" ]
   sources = [ "pw_fuzzer_disabled.cc" ]
   deps = [