sbbr/scripts/sbbr.bb: Replace legacy backticks with $(...)
sbbr/scripts/sbbr.bb: Replace legacy backticks with $(...)

ShellCheck (and others) consider backticks to be a legacy feature, and
prefer $(...) - https://github.com/koalaman/shellcheck/wiki/SC2006 .

Signed-off-by: Rebecca Cran <0ab09b420c3f4f686e1f6503c93d3111d2038689@nuviainc.com>

ARM-software/arm-enterprise-acs,ARM-software/arm-enterprise-acs,ARM-software/arm-enterprise-acs