bionic-amd64-tf-a-build: remove flexnet license variable

The variable ARMLMD_LICENSE_FILE is used by Arm products to point to
the (flexnet) license server [1], which  it is not needed during build
time. At run time, it is set by the CI [2,3] so remove this variable
from the Dockerfile.

[1] https://developer.arm.com/documentation/dui0040/d/apas05s01
[2] https://git.trustedfirmware.org/ci/tf-a-job-configs.git/tree/tf-a-builder.yaml#n41
[3] https://git.trustedfirmware.org/ci/tf-a-job-configs.git/tree/tf-a-builder/builders.sh#n162

Signed-off-by: Leonardo Sandoval <leonardo.sandoval@linaro.org>
Change-Id: Ia269115acae67ec7cbcb2c07796e1f2bf2a293a9
2 files changed