add py_cc_toolchain attribute

Author: rickeylev

python/private/py_cc_toolchain_rule.bzl

@@ -34,13 +34,24 @@ def _py_cc_toolchain_impl(ctx):
     else:
         libs = None
 
+    if ctx.attr.headers_abi3:
+        headers_abi3 = struct(
+            providers_map = {
+                "CcInfo": ctx.attr.headers_abi3[CcInfo],
+                "DefaultInfo": ctx.attr.headers_abi3[DefaultInfo],
+            },
+        )
+    else:
+        headers_abi3 = None
+
     py_cc_toolchain = PyCcToolchainInfo(
         headers = struct(
             providers_map = {
                 "CcInfo": ctx.attr.headers[CcInfo],
                 "DefaultInfo": ctx.attr.headers[DefaultInfo],
             },
         ),
+        headers_abi3 = headers_abi3,
         libs = libs,
         python_version = ctx.attr.python_version,
     )
@@ -61,6 +72,11 @@ py_cc_toolchain = rule(
             providers = [CcInfo],
             mandatory = True,
         ),
+        "headers_abi3": attr.label(
+            doc = ("Target that provides the Python ABI3 headers. Typically this " +
+                   "is a cc_library target."),
+            providers = [CcInfo],
+        ),
         "libs": attr.label(
             doc = ("Target that provides the Python runtime libraries for linking. " +
                    "Typically this is a cc_library target of `.so` files."),