🚚 Move toolchain registration to flake module (#260)

Hardcoding toolchain registrations into MODULE.bazel is a bad practice.

Moving it to the flake module makes the ll_toolchain optional and only
enables it on systems that can run Nix.

MODULE.bazel

@@ -4,8 +4,6 @@ module(
     compatibility_level = 0,
 )
 
-register_toolchains("@rules_ll//ll:ll_toolchain")
-
 # Platform support.
 bazel_dep(name = "platforms", version = "0.0.10")
 bazel_dep(name = "rules_cc", version = "0.0.17")
@@ -14,7 +12,10 @@ bazel_dep(name = "rules_cc", version = "0.0.17")
 bazel_dep(name = "bazel_skylib", version = "1.7.1")
 
 # Documentation.
-bazel_dep(name = "stardoc", version = "0.7.2", dev_dependency = True)
+#
+# TODO(aaronmondal): This should be a dev_dependency, but that currently breaks
+#                    the examples.
+bazel_dep(name = "stardoc", version = "0.7.2", dev_dependency = False)
 
 # TODO(aaronmondal): We don't actually use this. Fix LRE upstream to make this
 #                    import optional.

modules/rules_ll.nix

@@ -12,6 +12,8 @@ let
     # Add try-import %%workspace%%/ll.bazelrc to your .bazelrc to
     # include these flags when running Bazel in a nix environment.
 
+    build --extra_toolchains=@rules_ll//ll:ll_toolchain
+
     ${lib.concatLines processedActionEnvs}' >$out
   '';
 in