TCGETA, TCSETA, TCSETAF, TCSETAW termios ioctl no longer usable on all architectures with glibc 2.42

Bug report

Bug description:

The build of cpython is broken with glibc 2.42 on at least the alpha, hppa and sparc64 architectures, as reported for example on Gentoo: https://bugs.gentoo.org/962600, but also affecting Buildroot: https://autobuild.buildroot.net/results/e7d/e7d951b06e9338e622fe96b0fb02823b1ef5235c/build-end.log. The build failure looks like this:

./Modules/termios.c:1119:16: error: invalid application of 'sizeof' to incomplete type 'struct termio'
 1119 |     {"TCGETA", TCGETA},
      |                ^~~~~~
./Modules/termios.c:1131:16: error: invalid application of 'sizeof' to incomplete type 'struct termio'
 1131 |     {"TCSETA", TCSETA},
      |                ^~~~~~
./Modules/termios.c:1134:17: error: invalid application of 'sizeof' to incomplete type 'struct termio'
 1134 |     {"TCSETAF", TCSETAF},
      |                 ^~~~~~~
./Modules/termios.c:1137:17: error: invalid application of 'sizeof' to incomplete type 'struct termio'
 1137 |     {"TCSETAW", TCSETAW},
      |                 ^~~~~~~

The problem is that on those architectures, ioctls.h reference "struct termio", which has been removed from glibc 2.42. https://lists.gnu.org/archive/html/info-gnu/2025-07/msg00011.html.

While the issue is being fixed in the upstream Linux kernel, it will take time for those fixes to propagate, and a fix in Python would be relevant. PR coming.

CPython versions tested on:

3.13

Operating systems tested on:

Linux

Linked PRs

• gh-142380

Start in Modules/termios.c around the TCGETA, TCSETA, TCSETAF, and TCSETAW entries and review the glibc 2.42 failure on alpha, hppa, and sparc64. Reproduce the affected build if possible; done means CPython builds successfully on those architectures without the incomplete struct termio errors.