Fix build on non-glibc 32 bit architectures

[ii8]

No description provided.

[MatthewFluet]

Seems reasonable. I'm surprised that it isn't an issue on 64-bit platforms. I was playing around with a musl build on my amd64-linux Fedora machine, and I needed to avoid the #include <linux/types.h>.

Long term, I suspect that it would be better to clean up these platform files and eliminate the workarounds for outdated systems.

[ii8]

It's sometimes not an issue on 64 bit platforms because while the type is still defined twice, it will be 64 bits in both cases so the compiler doesn't mind. It's possible that it depends on the kernel version, some kernels will have __kernel_suseconds_t as 64 bits and others as 32 bits, only when it's different from the libc value does the error surface.

[MatthewFluet]

I suspect that what I ran into was a situation where the musl-gcc cross-compilation wrapper doesn't expose linux in the cpp #include path, but it is exposed under systems on which you were building.