fix(toolchain): attempt to fix the host toolchain on windows

Use the same binary path that the regular toolchain is using
in an attempt to see if the behaviour is any different.

Attempt to fix #1723

python/private/toolchains_repo.bzl

@@ -238,11 +238,16 @@ exports_files(["python"], visibility = ["//visibility:public"])
 
     (os_name, arch) = get_host_os_arch(rctx)
     host_platform = get_host_platform(os_name, arch)
+
+    is_windows = (os_name == WINDOWS_NAME)
+    python3_binary_path = "python.exe" if is_windows else "bin/python3"
+
     host_python = rctx.path(
         Label(
-            "@@{py_repository}_{host_platform}//:python".format(
+            "@@{py_repository}_{host_platform}//:{python}".format(
                 py_repository = rctx.attr.name[:-len("_host")],
                 host_platform = host_platform,
+                python = python3_binary_path,
             ),
         ),
     )