I can't speak for cmake but in autotools it's always just been "./configure --host=aarch64-linux-gnueabi" or whatever other target triplet is of relevance. It's similar in Meson.
The annoying factor is gathering the cross compiler and target dependencies, which is fortunately becoming easier with tools such as llvm/clang, and distros such as debian have always made huge efforts to facilitate it.
The annoying factor is gathering the cross compiler and target dependencies, which is fortunately becoming easier with tools such as llvm/clang, and distros such as debian have always made huge efforts to facilitate it.