It breaks when building with a gcc 4.9 host compiler.

force bash for command processing

on Ubuntu (14.04, 64 bit) /bin/sh refers to the dash shell.  The syntax

X+=Y

doesn't seem to be allowed by dash.  This minor fix forces bash to be
used instead.

This fixes some assertion failures when R_RISCV_64 and R_RISCV_CALL_PLT
were used against the same global symbol.

since we no longer use small PLTs.

The PLT bias broke under LD_BIND_NOW since the loader was unaware of the
value.  Secondarily, this avoids dependence on GP.  h/t Matt Thomas

Add -mno-rvm option to disable multiplier / division instructions (allows "M" extensions to be disabled)

The kernel and user now agree with each other, avoiding copies.
The zero register is no longer represented and is used to hold the pc.

We were relaxing them to JALR, but with a PC-relative offset,
rather than an absolute address.  That's now fixed.  We also
preferentially relax to JAL for these addresses when possible.

makes inline signature match regenerated signature from gperf

Add -mno-rvm option to disable multiplier / division instructions (allows "M" extensions to be disabled)

riscv: Add support for -mno-atomic to gcc and glibc.

When the flag is passed, atomic memory operations (RV32A, RV64A)
are avoided by gcc and glibc.  Atomic locking necessary for NPTL is
done via a new Linux system call.  Previous behavior utilizing
atomic memory instructions (i.e., -matomic) is the default.

This change is mutually dependent on the corresponding change to
riscv-linux.

This ensures proper recursive expansion of macros when the macros are not
defined in the order they are used.  Such as with the use of the macro
INTERNAL_SYSCALL, either directly or indirectly via another macro.

This is more in line with other ELF assemblers.  The old .set functionality
is now accessible via .option.

This needs to be implemented eventually.

The plan is to use LLVM to generate code for this nonstandard ISA extension.

Because of relaxations, GAS has better information about branch distances, and
so this improves code generation.  And it's simpler.