test: add system_python_nodeps_test (#3609)

Adds a simple system_python bootstrap test. Such a test otherwise
doesn't directly
exist, and only ends up accidentally tested by something in an example
directory.

Author: rickeylev

tests/bootstrap_impls/BUILD.bazel

@@ -13,6 +13,7 @@
 # limitations under the License.
 load("@rules_pkg//pkg:tar.bzl", "pkg_tar")
 load("@rules_shell//shell:sh_test.bzl", "sh_test")
+load("//python:py_test.bzl", "py_test")
 load("//tests/support:py_reconfig.bzl", "py_reconfig_binary", "py_reconfig_test")
 load("//tests/support:sh_py_run_test.bzl", "sh_py_run_test")
 load("//tests/support:support.bzl", "SUPPORTS_BOOTSTRAP_SCRIPT")
@@ -190,4 +191,12 @@ sh_test(
     }),
 )
 
+py_test(
+    name = "system_python_nodeps_test",
+    srcs = ["system_python_nodeps_test.py"],
+    config_settings = {
+        "//python/config_settings:bootstrap_impl": "system_python",
+    },
+)
+
 relative_path_test_suite(name = "relative_path_tests")

tests/bootstrap_impls/system_python_nodeps_test.py

@@ -0,0 +1 @@
+print("Hello, world")