Fix local external builds

- Remove internal only target from artifacts.tar
- Add clang-cl to the default windows platform constraints

Bug: b/345487703
Change-Id: I90951bc4da2b7f471bc981ca3758b863b1d63b31
Test: Ran full build locally
GitOrigin-RevId: aef5353029e2a0e1b24f5c5401613e6f3358a017

BUILD.bazel

@@ -17,6 +17,7 @@ platform(
     constraint_values = [
         "@platforms//cpu:x86_64",
         "@platforms//os:windows",
+        "@bazel_tools//tools/cpp:clang-cl",
     ],
     visibility = ["//visibility:public"],
 )
@@ -122,7 +123,6 @@ pkg_files(
     name = "artifacts_executable",
     srcs = [
         "//cmd/bootstrap",
-        "//cmd/credshelper",
         "//cmd/dumpstats",
         "//cmd/logdump",
         "//cmd/metricsuploader",