[chassis] add libffi-dev for sonic-utilities (sonic-net#15218)

In the PR sonic-net/sonic-utilities#2850 , for support remote access of linecards paramiko package is installed in sonic-utilities. libffi-dev needs to installed to be able to compile for armhf image

Signed-off-by: Arvindsrinivasan Lakshmi Narasimhan <arlakshm@microsoft.com>

files/build_templates/sonic_debian_extension.j2

@@ -207,6 +207,9 @@ sudo LANG=C DEBIAN_FRONTEND=noninteractive chroot $FILESYSTEM_ROOT apt-get -y in
 # Install prerequisites needed for using the Python m2crypto package, used by sonic-utilities
 sudo LANG=C DEBIAN_FRONTEND=noninteractive chroot $FILESYSTEM_ROOT apt-get -y install openssl
 
+# install libffi-dev to match utilities' dependency.
+sudo LANG=C DEBIAN_FRONTEND=noninteractive chroot $FILESYSTEM_ROOT apt-get -y install libffi-dev
+
 # Install SONiC Utilities Python package
 SONIC_UTILITIES_PY3_WHEEL_NAME=$(basename {{sonic_utilities_py3_wheel_path}})
 sudo cp {{sonic_utilities_py3_wheel_path}} $FILESYSTEM_ROOT/$SONIC_UTILITIES_PY3_WHEEL_NAME