feat: expose @nodejs_host//:bin/node without using alias (#3434)

This makes it possible for repository rules to reliably find a path to a node interpreter using rctx.path,
without having to hard-code any repository name.
Needed to workaround rctx.path not understanding alias, and repository rules not having any toolchain resolution.

Author: alexeagle

nodejs/private/nodejs_repo_host_os_alias.bzl

@@ -1,8 +1,10 @@
 "Provide convenience repository for the host platform"
 
-load("//nodejs/private:os_name.bzl", "os_name")
+load("//nodejs/private:os_name.bzl", "is_windows_os", "os_name")
 
 def _nodejs_host_os_alias_impl(repository_ctx):
+    ext = ".exe" if is_windows_os(repository_ctx) else ""
+
     # Base BUILD file for this repository
     repository_ctx.file("BUILD.bazel", """# Generated by nodejs_repo_host_os_alias.bzl
 package(default_visibility = ["//visibility:public"])
@@ -18,12 +20,22 @@ alias(name = "node",                    actual = "@{node_repository}_{os_name}//
 alias(name = "npm",                     actual = "@{node_repository}_{os_name}//:npm")
 alias(name = "node_files",              actual = "@{node_repository}_{os_name}//:node_files")
 alias(name = "npm_files",               actual = "@{node_repository}_{os_name}//:npm_files")
-exports_files(["index.bzl"])
+exports_files([
+    "index.bzl",
+    "bin/node{ext}",
+])
 """.format(
         node_repository = repository_ctx.attr.user_node_repository_name,
         os_name = os_name(repository_ctx),
+        ext = ext,
     ))
 
+    repository_ctx.symlink("../{node_repository}_{os_name}/bin/node{ext}".format(
+        node_repository = repository_ctx.attr.user_node_repository_name,
+        os_name = os_name(repository_ctx),
+        ext = ext,
+    ), "bin/node" + ext)
+
     # index.bzl file for this repository
     repository_ctx.file("index.bzl", content = """# Generated by nodejs_repo_host_os_alias.bzl
 host_platform="{host_platform}"