ARM 32-bit runs out of registers for inline assembly

[albinahlback]

Possibly related: We got the following on the armhf build of the Debian package of flint 3.3.1:

  CC  fmpz_mod/ctx.c
In file included from /build/reproducible-path/flint-3.3.1/src/longlong.h:50,
                 from /build/reproducible-path/flint-3.3.1/src/fmpz_poly/taylor_shift_horner.c:13:
/build/reproducible-path/flint-3.3.1/src/fmpz_poly/taylor_shift_horner.c: In function ‘_fmpz_poly_taylor_shift_horner’:
/build/reproducible-path/flint-3.3.1/src/longlong_asm_gcc.h:266:3: error: ‘asm’ operand has impossible constraints or there are not enough registers
  266 |   __asm__("adds %2,%5,%8\n" \
      |   ^~~~~~~
/build/reproducible-path/flint-3.3.1/src/fmpz_poly/taylor_shift_horner.c:143:21: note: in expansion of macro ‘add_sssaaaaaa’
  143 |                     add_sssaaaaaa(t[3 * j + 2], t[3 * j + 1], t[3 * j],
      |                     ^~~~~~~~~~~~~
  CC  fmpz_mod/discrete_log_pohlig_hellman.c

Full log: https://buildd.debian.org/status/fetch.php?pkg=flint&arch=armhf&ver=3.3.1-1~exp1&stamp=1756320704&file=log

Originally posted by @d-torrance in #2380