https://gitlab.kitware.com/cmake/community/-/wikis/doc/cmake/CrossCompiling has:
Once the system and the compiler are determined by CMake, it loads the
corresponding files in the following order:
Platform/${CMAKE_SYSTEM_NAME}.cmake (optional, but issues a stern
warning)
Platform/${CMAKE_SYSTEM_NAME}-.cmake
(optional)
Platform/${CMAKE_SYSTEM_NAME}--${CMAKE_SYSTEM_PROCESSOR}.cmake
(optional)
is either the basename of the compiler executable, e.g. "gcc"
(this is also used if gcc has a different name) or "cl", or by a
compiler id, which is detected by compiling a test source file.
It looks as if some text has disappeared (e.g. after the -
and before the " is" in the final paragraph.