perfetto: Disable -Wshadow-uncaptured-local

-Wshadow-uncaptured-local is a new warning (not enabled by default)
in clang which is enabled by -Weverything. Disable it to fix
ChromeOS ToT llvm builds.

Bug: b:278327944
Test: perfetto builds with ToT llvm
Change-Id: I254737f8d4061d5f7e142b7da04dc0d6145ed23d
diff --git a/gn/standalone/BUILD.gn b/gn/standalone/BUILD.gn
index 5c7de64..d000f53 100644
--- a/gn/standalone/BUILD.gn
+++ b/gn/standalone/BUILD.gn
@@ -82,6 +82,7 @@
       "-Wno-poison-system-directories",
       "-Wno-reserved-id-macro",
       "-Wno-reserved-identifier",
+      "-Wno-shadow-uncaptured-local",
       "-Wno-unknown-sanitizers",
       "-Wno-unknown-warning-option",
       "-Wno-unsafe-buffer-usage",