crossystem: Make crossystem vendor_available Making crossystem `vendor_available` instead of `vendor` means it can be installed in /system/bin/ or /vendor/bin/ depending on which target is used, `crossystem` or `crossystem.vendor` respectively. BUG=b:374130759 TEST=Build BRANCH=None Change-Id: I9a27f92c975b23d95f9e8dbb9d2189a1cd7518d2 Signed-off-by: Rob Barnes <[email protected]> Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/5979089 Tested-by: Jakub Czapiga <[email protected]> Reviewed-by: Jakub Czapiga <[email protected]> Commit-Queue: Jakub Czapiga <[email protected]>