bionic-amd64-tf-m-build: Download multi versions of compilers

TF-M Open CI needs to support multi versions of compilers.
Download all compilers to COMPILER_DIR, and set specific paths
for different compiler versions. So that the compiler versions
can be selected in every single build-config job.

Currently following compilers are installed for TF-M Open CI:
    - GCC v7.3.1
    - GCC v10.3
    - ARMClang v6.13

Signed-off-by: Xinyu Zhang <xinyu.zhang@arm.com>
Change-Id: I31cc55181704319d5194c336c5bd6f14fccd921e
3 files changed