The first commit just switches to calling the functions defined in libc instead of trying to link against them directly. This fixes the first issue on some platforms like illumos/solaris where cfmakeraw isn't defined but libc includes a shim.
The second commit uses the constant TCSANOW instead of hardcoding it since it is 0 on Linux but not all other platforms. (Also use STDOUT_FILENO for consistency).
With these two fixes, cargo test passes for me without a linker error (first issue) or failing with invalid argument (second issue).