This patch set allow target to use customized multi-lib mechanism rather than the built-in multi-lib mechanism.
The motivation of this patch is RISC-V might have very complicated multi-lib re-use rule*, which is hard to maintain and use current multi-lib scripts, we even hit the "argument list too long" error when we tried to add more multi-lib reuse rule. * Here is an example for RISC-V multi-lib rules: https://gist.github.com/kito-cheng/0289cd42d9a756382e5afeb77b42b73b V2 Changes: - NO changes for first patch(TARGET_COMPUTE_MULTILIB part) since first version. - Handle option other than -march and -mabi for riscv_compute_multilib.
