message: CMake: improved message about the target CPU detection
diff: @@ -66,6 +66,12 @@ else()
  set(ARCH 32 CACHE INTERNAL "32-bit architecture")
  endif()
  +# When not cross-compiling, CMAKE_SYSTEM_PROCESSOR has the same value as the CMAKE_HOST_SYSTEM_PROCESSOR variable.
  +# In many cases, this will correspond to the target architecture for the build, but this is not guaranteed.
  +# (E.g. on Windows, the host may be AMD64 even when using a MSVC cl compiler with a 32-bit target.)
  +# When cross-compiling, a CMAKE_TOOLCHAIN_FILE should set the CMAKE_SYSTEM_PROCESSOR variable to match target
  +# architecture that it specifies.
  +if(CMAKE_SYSTEM_PROCESSOR)
  if(("${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "x86") OR ("${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "amd") OR
  ("${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "X86") OR ("${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "AMD"))
  set(TARGET_CPU x86) # Emscripten
  @@ -80,6 +86,9 @@ elseif(("${CMAKE_SYSTEM_PROCESSOR}" MATCHES "arm") OR ("${CMAKE_SYSTEM_PROCESSOR
  else()
  message("Unknown system processor: " ${CMAKE_SYSTEM_PROCESSOR})
  endif()
  +else()
  + message("Unable to detect target processor: CMAKE_SYSTEM_PROCESSOR is not defined")
  +endif()
  if(TARGET_CPU)
  message("Target processor: " ${TARGET_CPU})
  