[RISCV] Support RISC-V Profiles in -march option (#76357)
This PR implements the draft
https://github.com/riscv-non-isa/riscv-toolchain-conventions/pull/36.
Currently, we replace specified profile in `-march` with standard
arch string.
This is recommitted as 66f88de was reverted because of failures
caused by lacking `--target` option.
