[llvm] [TableGen] Detect invalid -D arguments and fail. (PR #102813)

[Rahul Joshi via llvm-commits]

jurahul wrote:

Note, linux build failure looks like an infra issue:

```
BUILDKITE_REPO: https://github.com/llvm/llvm-project.git
--
  | fatal: not a git repository (or any parent up to mount point /var/lib)
  | Stopping at filesystem boundary (GIT_DISCOVERY_ACROSS_FILESYSTEM not set).
  | current remote URL: not a git repo
  | Remote URL does not match. Deleting and recreating the directory.
  | rm: cannot remove '/var/lib/buildkite-agent/builds/linux-56-59b8f5d88-876rk-1/llvm-project/github-pull-requests/build/test/tools/llvm-ifs/Output/fail-file-write.test.tmp.TestDir/Output.TestFile': Permission denied
  | 🚨 Error: The global pre-checkout hook exited with status 1
```

I don't have permission to retrigger the build, but I am assuming it will happen when I rebase the branch (right now its up-to-date with main, so when some commits go in). 


https://github.com/llvm/llvm-project/pull/102813