[PATHCH] Disable inline asm for in-tree mpfr (PR69134)

[Matthew Fortune]

Bernd Edlinger <bernd.edlinger@hotmail.de> writes:
> an in-tree mpfr build enables inline asm code, which makes the mips-bootstrap fail,
> because at least mpfr 2.4.2 uses the "=h" constraint but in config/mips/constraints.md
> we find: "Formerly the @code{hi} register.  This constraint is no longer supported.".
> 
> Using asm code is generally not desirable for in-tree mpfr builds.  So I looked for a way
> to disable the asm code, and found it can be done, but differently than for in-tree gmp.
> See the attached patch.
> 
> 
> Boot-strapped and Reg-tested on x86_64-pc-linux-gnu.
> OK for trunk?

FWIW, this sounds like a good plan to me. I'll try and remember to ask someone to work
through MPFR to fix the inline asm for MIPS.

Matthew