jammy-amd64-tf-a-build-next: add clang-18

Add clang18.1.18 to the staging area to test its
use in the TF-A CI.

This is needed to upgrade hafnium build to clang-18.

Signed-off-by: J-Alves <joao.alves@arm.com>
Change-Id: I62e52a55b0e1a2b8e0a971ac68a4244c7ed72429
1 file changed