Document how to use LLDB in the Slang codebase (#7809)

* Document how to use LLDB in the Slang codebase

* Include `slang_lldb.py` in `.lldbinit`

* Switch from GCC to Clang

* Include a VS Code task to build before debugging

* Fix clangd

1 files changed, 11 insertions, 3 deletions

diff --git a/flake.nix b/flake.nix
index a6ad8f9f5..5b63b0e4c 100644
--- a/flake.nix
+++ b/flake.nix
@@ -16,12 +16,20 @@
         pkgs = import nixpkgs { inherit system; };
       in
       {
-        devShell = pkgs.mkShell {
+        # We want to use Clang instead of GCC because it seems to behave better
+        # with LLDB, so we use `mkShellNoCC` here instead of `mkShell` because
+        # the latter brings in GCC by default on Linux.
+        devShell = pkgs.mkShellNoCC {
           buildInputs = [
+            # Must put `clang-tools` before `clang` for clangd to work properly.
+            # We use `llvmPackages_17.clang-tools` instead of just `clang-tools`
+            # to match the `clang-format` version used in CI.
+            pkgs.llvmPackages_17.clang-tools
+
+            pkgs.clang
             pkgs.cmake
             pkgs.gersemi
-            pkgs.llvm
-            pkgs.llvmPackages_17.clang-tools
+            pkgs.lldb
             pkgs.ninja
             pkgs.nixfmt-rfc-style
             pkgs.prettier