[clang-tools-extra] [clang-tidy] add option to avoid "no checks enabled" error (PR #96122)

[Danny Mösch via cfe-commits]

================
@@ -325,6 +325,14 @@ option is recognized.
 )"),
                                   cl::init(false), cl::cat(ClangTidyCategory));
 
+static cl::opt<bool> AllowEmptyCheckList("allow-empty-checks", desc(R"(
----------------
SimplyDanny wrote:

Should the option names be in sync?
```suggestion
static cl::opt<bool> AllowEmptyCheckList("allow-empty-check-list", desc(R"(
```
or
```suggestion
static cl::opt<bool> AllowEmptyChecks("allow-empty-checks", desc(R"(
```

https://github.com/llvm/llvm-project/pull/96122