Update Fuchsia os constraint.
diff --git a/BUILD.bazel b/BUILD.bazel
index 6d9cc98..7573369 100644
--- a/BUILD.bazel
+++ b/BUILD.bazel
@@ -58,7 +58,7 @@
 
 config_setting(
     name = "fuchsia",
-    values = {"crosstool_top": "@fuchsia_clang//:toolchain"},
+    constraint_values = ["@platforms//os:fuchsia"],
 )
 
 config_setting(