Which OS? Do you have an POSIX-like environment available? As others have said, on Windows you can run it and check Task Manager. If you have a POSIX-like environment, you can use the file utility:
On Windows with MSYS2:
Code:
$ file build/mingw-gcc/bin/x64/Debug/sdlmame64d.exe
build/mingw-gcc/bin/x64/Debug/sdlmame64d.exe: PE32+ executable (console) x86-64, for MS Windows
On Linux:
Code:
$ file build-clang/linux_clang/bin/x64/Debug/mame64d
build-clang/linux_clang/bin/x64/Debug/mame64d: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/l, for GNU/Linux 3.2.0, BuildID[sha1]=bfd4c8fc389501e64a8e6f66c2356b6ad218e7ab, with debug_info, not stripped