[fuchsia] Exclude cronet targets from the build

Bug: 1290522
Change-Id: I174c43b673db44e96d934bf580d9f964737dbc8e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3662331
Reviewed-by: Bruce Dawson <brucedawson@chromium.org>
Reviewed-by: Fabrice de Gans <fdegans@chromium.org>
Commit-Queue: Joseph Wang <jwx@google.com>
Cr-Commit-Position: refs/heads/main@{#1006938}

diff --git a/BUILD.gn b/BUILD.gn
index 95505cf6..e472f3b 100644
--- a/BUILD.gn
+++ b/BUILD.gn

@@ -223,7 +223,7 @@
     }
   }
 
-  if (!is_ios && !is_android) {
+  if (!is_ios && !is_android && !is_fuchsia) {
     deps += [ "//components/viz/demo:viz_demo" ]
     if (!use_libfuzzer) {
       # TODO(crbug.com/1241949): libcronet.$version.so fails to link in libfuzzer builds.