Support older linux kernel in glibc

[cooperq]

Right now your toolchain is set to compile only for linux kernel 5.10 or later. It would be good to pick an older kernel, perhaps 3.2, as your compile target for those of us who are trying to compile for older targets, such as embedded arm systems. I am specifically requesting this for the arm7-unknown-linux-gnueabihf if it makes a difference. Happy to provide a PR for this.

[messense]

See also #39, there are conflict requirments. But it's probably ok to lower it for armv7. PR welcome.

[cooperq]

actually since this is just for use on my project which supports strange old hardware https://github.com/efforg/rayhunter I think it's probably not worth making a PR which will potentially break other people's projects, probably just better for me to fork the code. Thanks!

[cooperq]

Reopening because the build job failed on my fork so maybe its best to just do it here instead 😩 I have opened a PR.