Fix windows toolchain target_compatible_with (#1616)

It seems like this was incorrectly targeting apple constraints, when
really if this works at all today it will only be able to build windows
targets for now.

Fixes #1614

Author: keith

swift/internal/swift_autoconfiguration.bzl

@@ -364,7 +364,10 @@ toolchain(
         "@platforms//os:windows",
         "@platforms//cpu:x86_64",
     ],
-    target_compatible_with = APPLE_PLATFORMS_CONSTRAINTS[arch],
+    target_compatible_with = [
+        "@platforms//os:windows",
+        "@platforms//cpu:x86_64",
+    ],
     toolchain = ":windows-toolchain",
     toolchain_type = "{toolchain_type}",
     visibility = ["//visibility:public"],