arc-setup: fix fuzzer builds

Fix a config error in GN build.
sources assignment should be inside executable.

BUG=chromium:1159646
TEST=local build

Change-Id: Id7bd1381523e550cc725d977c5b4ad3c5c3af2a0
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform2/+/2596026
Tested-by: Manoj Gupta <manojgupta@chromium.org>
Auto-Submit: Manoj Gupta <manojgupta@chromium.org>
Reviewed-by: Tatsuhisa Yamaguchi <yamaguchi@chromium.org>
Reviewed-by: Hidehiko Abe <hidehiko@chromium.org>
Commit-Queue: Tatsuhisa Yamaguchi <yamaguchi@chromium.org>
diff --git a/arc/setup/BUILD.gn b/arc/setup/BUILD.gn
index c0594d9..f3cfc3e 100644
--- a/arc/setup/BUILD.gn
+++ b/arc/setup/BUILD.gn
@@ -182,8 +182,8 @@
 }
 
 if (use.fuzzer) {
-  sources = [ "arc_setup_util_find_all_properties_fuzzer.cc" ]
   executable("arc_setup_util_find_all_properties_fuzzer") {
+    sources = [ "arc_setup_util_find_all_properties_fuzzer.cc" ]
     configs += [
       "//common-mk/common_fuzzer",
       ":target_defaults",