ArmVirtPkg: increase FD/FV size for NOOPT builds

ArmVirtPkg: increase FD/FV size for NOOPT builds

After upgrading the CI system we use for building the ArmVirtPkg
targets, we started seeing failures due to the NOOPT build running
out of space when using the CLANG38 toolchain definition combined
with clang 7.

We really don't want to increase the FD/FV sizes in general to
accommodate this, so parameterize the relevant quantities and
increase them by 50% for NOOPT builds.

Reviewed-by: Philippe Mathieu-Daude <philmd@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>