Shameless plug: Some of my hobby projects written in C (e.g. https://github.com/pts/bakefat) can be built reproducibly for Linux >=1.0 (1994), FreeBSD (same ELF executable program file as for Linux) and Win32 working on all versions of Windows (Windows NT 3.1 (1993)--Windows 11). The C compiler (running on Linux i386 and amd64 host) used for the release build is self-contained and included in the project, along with the libc.

Doing such backward compatibility is definitiely possible for command-line tools. Once set up, it's automatic, and it needs extra testing after major changes.