scripts: gki: Add LD to make args to enable CFI/LTO

Include LD also as a make argument to enable CFI to satisfy the
ld.lld requirement in order to enable CONFIG_LD_IS_LLD.

Change-Id: I1ffa90fd88cbd2e953137380186e30cfd4e12b16
Signed-off-by: Prakruthi Deepak Heragu <pheragu@codeaurora.org>