busybox.inc: Fix bashism in compile, which fixes sh being suid
Fix the bashism in the suid check. This ensures that the check works
correctly on hosts that default sh to e.g. dash. If this check fails the
suid shell workaround does not remove sh from the suid binary and
results in the target system containing a busybox.suid with sh as well
as /bin/sh -> /bin/busybox.suid.
Signed-off-by: Nathan Rossi <nathan@nathanrossi.com> Cc: Andrej Valek <andrej.valek@siemens.com> Cc: Radovan Scasny <radovan.scasny@siemens.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
