feat(pypi): support aarch64 windows on pipstar

This adds the necessary bits for Windows ARM64 support when evaluating
env markers in requirements files and selecting the right wheels in
`experimental_index_url`.

Related #2276

Author: aignas

CHANGELOG.md

@@ -129,6 +129,9 @@ END_UNRELEASED_TEMPLATE
   * {obj}`//python:features.bzl%features.headers_abi3` can be used to
     feature-detect the presense of the above.
 * (toolchains) Local toolchains can use a label for the interpreter to use.
+* (pypi) Support for environment marker and `experimental_index_url` handling for
+  Windows ARM64
+  ([#2276](https://github.com/bazel-contrib/rules_python/issues/2276)).
 
 {#v1-6-3}
 ## [1.6.3] - 2025-09-21

MODULE.bazel

@@ -163,6 +163,7 @@ pip = use_extension("//python/extensions:pip.bzl", "pip")
         whl_platform_tags = whl_platform_tags,
     )
     for cpu, whl_platform_tags in {
+        "aarch64": ["win_arm64"],
         "x86_64": ["win_amd64"],
     }.items()
     for freethreaded in [

examples/bzlmod/MODULE.bazel

@@ -172,7 +172,7 @@ pip.default(
     os_name = "windows",
     platform = "windows_aarch64",
     whl_abi_tags = [],  # default to all ABIs
-    whl_platform_tags = ["win_amd64"],
+    whl_platform_tags = ["win_arm64"],
 )
 
 # To fetch pip dependencies, use pip.parse. We can pass in various options,