[Tf-m] Required GCC tools for reference implementation

Is there a compelling reason that the reference implementation of the PSA requires the use of the gcc-arm-none-eabi-6-2017-q1-update gnu tools?

The linker in these tools generates a non-standard s_veneers.o file that cannot be consumed by some CLANG linkers. It should be a relocatable object file with absolute symbols, but instead it's static executable file.

If I use a newer GCC linker (ie: gcc-arm-none-eabi-7-2017-q4-major) for the final link of the secure image, the generated s_veneers.o file is of the correct type.

Alan DeMars