Add alias forwarding internal @nanobind to users

[nicholasjng]

This enables users to consume the internal nanobind library for their own purposes, exposing it as @nanobind_bazel//:nanobind.

Related to #48.

[nicholasjng]

cc @hawkinsp

I was able to use this to build a target off the nanobind example's bazel branch with this patch:

diff --git a/MODULE.bazel b/MODULE.bazel
index e1f5903..a15a36b 100644
--- a/MODULE.bazel
+++ b/MODULE.bazel
@@ -1,6 +1,10 @@
 module(name = "nanobind_example", version = "0.1.0")
 
-bazel_dep(name = "nanobind_bazel", version = "2.2.0")
+bazel_dep(name = "nanobind_bazel", version = "")
+local_path_override(
+    module_name = "nanobind_bazel",
+    path = "../nanobind-bazel",
+)
 bazel_dep(name = "rules_python", version = "1.0.0")
 
 python = use_extension("@rules_python//python/extensions:python.bzl", "python")
diff --git a/setup.py b/setup.py
index 6584bab..82a9d25 100644
--- a/setup.py
+++ b/setup.py
@@ -58,7 +58,7 @@ class BuildBazelExtension(build_ext.build_ext):
 
         bazel_argv = [
             "bazel",
-            "run",
+            "build",
             ext.bazel_target,
             f"--symlink_prefix={temp_path / 'bazel-'}",
             f"--compilation_mode={'dbg' if self.debug else 'opt'}",
@@ -115,7 +115,7 @@ setuptools.setup(
     ext_modules=[
         BazelExtension(
             name="nanobind_example.nanobind_example_ext",
-            bazel_target="//src:nanobind_example_ext_stubgen",
+            bazel_target="//src:foo",
             free_threaded=free_threaded,
             py_limited_api=py_limited_api,
         )
diff --git a/src/BUILD b/src/BUILD
index 5562dca..70b6a60 100644
--- a/src/BUILD
+++ b/src/BUILD
@@ -20,6 +20,12 @@ nanobind_stubgen(
     name = "nanobind_example_ext_stubgen",
     module = ":nanobind_example_ext",
     marker_file = "src/py.typed",
-    output_directory = "src",
-    recursive = True,
+#    output_directory = "src",
+#    recursive = True,
 )
+
+cc_library(
+    name = "foo",
+    srcs = ["nanobind_example_ext.cpp"],
+    deps = ["@nanobind_bazel//:nanobind"],
+)

Assuming that you have a local nanobind_bazel checked out on the same directory level as the nanobind_example.

[nicholasjng]

I'm going to merge this now, so that you can already use the alias e.g. by declaring nanobind_bazel as a git_override.

The label flag feature is still pending, in case you would like to use a completely custom @nanobind repo at some point in the future (you could also just patch the nanobind.BUILD, though).