aemfvp-a: add fetch-tools.sh in in build-test-uefi.sh

Make sure that aemfvp-a/fetch-tools.sh is executed by
build-test-uefi.sh so compilers and other dependency are downloaded.

Signed-off-by: Patrik Berglund <patrik.berglund@arm.com>
Change-Id: Ifc93750ebec37721913e5e4a8f47529cb266772f