Introduce bazel_ot package

This is bazelisk with auto completion stolen from bazel package.

dev/opentitan.nix

@@ -1,5 +1,6 @@
 {
   pkgs,
+  bazel_ot,
   python_ot,
   verilator_ot,
   ncurses5,
@@ -29,8 +30,7 @@ in
     targetPkgs = _:
       with pkgs;
         [
-          bazelisk
-
+          bazel_ot
           python_ot
           verilator_ot
 

flake.nix

@@ -30,7 +30,7 @@
       packages = import ./pkgs {inherit pkgs inputs;};
       devShells = {
         opentitan = pkgs.callPackage ./dev/opentitan.nix {
-          inherit (packages) verilator_ot python_ot;
+          inherit (packages) bazel_ot verilator_ot python_ot;
         };
       };
       formatter = pkgs.alejandra;

pkgs/bazel_ot/default.nix

@@ -0,0 +1,20 @@
+{
+  runCommand,
+  bazelisk,
+  bazel_6,
+  ...
+}:
+# OpenTitan requires a specific version of Bazel.
+# We *could* package our own Bazel, but it can't be a simple override since Bazel build process
+# require a lot of Internet dependencies.
+#
+# For simplicity we'll just let bazelisk do the heavyloading.
+#
+# This package basically just creates an alias from bazel to bazelisk and adds the auto completion
+# which is absent in bazelisk.
+runCommand "bazel" {} ''
+  cp -r ${bazelisk} $out
+  chmod -R +w $out
+  ln -s $out/bin/bazelisk $out/bin/bazel
+  cp -r ${bazel_6}/share $out/share
+''

pkgs/default.nix

@@ -9,6 +9,7 @@
 {
   verilator_ot = import ./verilator {inherit pkgs;};
   python_ot = pkgs.callPackage ./python_ot {inherit inputs;};
+  bazel_ot = pkgs.callPackage ./bazel_ot {};
 }
 // pkgs.lib.optionalAttrs (pkgs.system == "x86_64-linux") {
   lowrisc-toolchain-gcc-rv32imcb = pkgs.callPackage ./lowrisc-toolchain-gcc-rv32imcb.nix {};