strcat() is a C Standard Library function. As such, the prototype for this and all other C Standard Library functions, will be the same on Windows, Linux, UNIX, MacOS, and all other Standards Compliant compilers, on any O/S. No need to post it here.
You can see the prototype for strcat() and all other Standard Library functions, online, by typing in"man strcat" (Or any other function), in any browser! (Use man7.org, and stay away from die.net, which has not been updated for many years!)