[gn build] assert clang-format does not depend on AST, Frontend, Sema at gn time

To catch things like https://reviews.llvm.org/D69854 and
https://reviews.llvm.org/D89708 earlier next time they happen.

utils/gn/secondary/clang/tools/clang-format/BUILD.gn

@@ -7,5 +7,10 @@ executable("clang-format") {
     "//clang/lib/Tooling/Core",
     "//llvm/lib/Support",
   ]
+  assert_no_deps = [
+    "//clang/lib/AST/",
+    "//clang/lib/Frontend/",
+    "//clang/lib/Sema/",
+  ]
   sources = [ "ClangFormat.cpp" ]
 }