[gn] port f65c199

Author: nico

llvm/utils/gn/secondary/clang-tools-extra/clangd/test/BUILD.gn

@@ -39,6 +39,7 @@ write_lit_config("lit_site_cfg") {
     "CLANGD_ENABLE_REMOTE=0",
     "CLANGD_TIDY_CHECKS=1",
     "LLVM_HOST_TRIPLE=$llvm_current_triple",
+    "LLVM_INCLUDE_BENCHMARKS=",
     "LLVM_LIT_TOOLS_DIR=",  # Intentionally empty, matches cmake build.
     "LLVM_TOOLS_DIR=" + rebase_path("$root_out_dir/bin"),
     "LLVM_TARGET_TRIPLE=$llvm_target_triple",