fip: modify build.sh the script [1/1]

PD#SWPL-72235

Problem:
the Bash if has error,when the judgment does not hold

Solution:
modify build.sh the script for a5/s4/t3/t7

Verify:
Compile pass.

Change-Id: Ia65a88c983a22faf2d5a8682b808950d8be4e212
Signed-off-by: Meng Yu <meng.yu@amlogic.com>
4 files changed