[bazel] Add os select for plugin process on Initialization target to add windows (#211276)
Another small piece of windows build support for LLDB in bazel.
Internally at Meta, our buck2 rule for this has a split for mac/linux
with PluginProcessPOSIX and windows with PluginProcessWindowsCommon. So
this should be a no-op for existing linux & mac builds while setting up
a bit more for windows.
I have no bazel build set up locally, so will wait on CI to confirm no
regression.
bazel rule creation assisted with claude