pw_env_setup: Windows target support packages

Include target support packages when bootstrapping on Windows. This also
affects downstream projects that directly invoke Pigweed's
bootstrap.bat, including the sample project. Longer-term those projects
need to do something equivalent to the POSIX bootstrap.

Change-Id: Idf0bfe40d8611e2d2769604e67ee97a2730d6af8
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/24106
Commit-Queue: Rob Mohr <mohrr@google.com>
Pigweed-Auto-Submit: Rob Mohr <mohrr@google.com>
Reviewed-by: Anthony DiGirolamo <tonymd@google.com>
diff --git a/bootstrap.bat b/bootstrap.bat
index 57f89fe..29146b6 100644
--- a/bootstrap.bat
+++ b/bootstrap.bat
@@ -112,6 +112,7 @@
     --shell-file "%shell_file%" ^
     --install-dir "%_PW_ACTUAL_ENVIRONMENT_ROOT%" ^
     --use-pigweed-defaults ^
+    --virtualenv-gn-target "%PW_ROOT%#:target_support_packages.install" ^
     --project-root "%PW_PROJECT_ROOT%"
 goto activate_shell