scripts: setup_board: Run in chroot if required

SetupBoard only works in the chroot, and will error if run outside.
To be user friendly, just enter the chroot if the user isn't in it.

BUG=b:279206393
TEST=setup_board --board amd64-generic --force
     (outside chroot)

Change-Id: Iea86216ee5633eaedfac1da13c629006c1b3e8b0
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/4459918
Commit-Queue: Jack Rosenthal <jrosenth@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
Auto-Submit: Jack Rosenthal <jrosenth@chromium.org>
Tested-by: Jack Rosenthal <jrosenth@chromium.org>
diff --git a/scripts/setup_board.py b/scripts/setup_board.py
index b6a939c..b2b5516 100644
--- a/scripts/setup_board.py
+++ b/scripts/setup_board.py
@@ -220,6 +220,7 @@
 
 
 def main(argv):
+    commandline.RunInsideChroot()
     opts = _ParseArgs(argv)
     try:
         sysroot.SetupBoard(