1.10, 1.11, 1.12)
  -mabi=ABI                   set the RISC-V ABI
  -mrelax                     enable relax (default)
  -mno-relax                  disable relax
  -march-attr                 generate RISC-V arch attribute
  -mno-arch-attr              don't generate RISC-V arch attribute
  -mcsr-check                 enable the csr ISA and privilege spec version checks
  -mno-csr-check              disable the csr ISA and privilege spec version checks (default)
  -mbig-endian                assemble for big-endian
  -mlittle-endian             assemble for little-endian