[circt-verilog-lsp] Add -C command line option

This PR extends the CIRCT Verilog LSP server with support for project command files (`-C` / `--command-file`) and improves robustness around source locations and diagnostics.

- **Command file support**
  - Added `commandFiles` option to `VerilogServerOptions`.
  - Extended the CLI with `-C`/`--command-file` flags to pass one or more command files.
  - Each buffer’s `Driver` now processes command files, filtering out the current main buffer to avoid duplication.
  - Implemented `removeFileToTemp` helper to strip the main file from command files and materialize a temporary version.

- **Source location handling**
  - Improved absolute/real path resolution when constructing LSP URIs.
  - Fallbacks added for when `slang::SourceManager` has no full path info.

- **Compilation setup**
  - Ensure all definitions in the buffer/project scope are treated as top modules.

- **Indexing improvements**
  - Skip top instances not defined in the current file.
  - Added guards against invalid or empty ranges (especially macro expansions).

Author: Scheremo

include/circt/Tools/circt-verilog-lsp-server/CirctVerilogLspServerMain.h

@@ -35,13 +35,17 @@ namespace circt {
 namespace lsp {
 struct VerilogServerOptions {
   VerilogServerOptions(const std::vector<std::string> &libDirs,
-                       const std::vector<std::string> &extraSourceLocationDirs)
-      : libDirs(libDirs), extraSourceLocationDirs(extraSourceLocationDirs) {}
+                       const std::vector<std::string> &extraSourceLocationDirs,
+                       const std::vector<std::string> &commandFiles)
+      : libDirs(libDirs), extraSourceLocationDirs(extraSourceLocationDirs),
+        commandFiles(commandFiles) {}
   /// Additional list of RTL directories to search.
   const std::vector<std::string> &libDirs;
-
   /// Additional list of external source directories to search.
   const std::vector<std::string> &extraSourceLocationDirs;
+  /// Additional list of command files that reference dependencies of the
+  /// project.
+  const std::vector<std::string> &commandFiles;
 };
 // namespace lsp
 

lib/Tools/circt-verilog-lsp-server/LSPServer.cpp

@@ -8,6 +8,7 @@
 
 #include "LSPServer.h"
 #include "VerilogServerImpl/VerilogServer.h"
+#include "llvm/Support/JSON.h"
 #include "llvm/Support/LSP/Protocol.h"
 #include "llvm/Support/LSP/Transport.h"
 #include <optional>