Build: Support CMAKE_OSX_ARCHITECTURES

... as long as it contains only a singular value, which must equal
"x86_64", "arm64", "i386", or "ppc".

CMakeLists.txt

@@ -127,9 +127,6 @@ foreach(dir ${DIRLIST})
 endforeach()
 
 # Detect CPU type and word size
-if(CMAKE_OSX_ARCHITECTURES MATCHES "ppc")
-	set(CMAKE_SYSTEM_PROCESSOR ppc)
-endif()
 math(EXPR BITS "${CMAKE_SIZEOF_VOID_P} * 8")
 string(TOLOWER ${CMAKE_SYSTEM_PROCESSOR} CMAKE_SYSTEM_PROCESSOR_LC)
 if(CMAKE_SYSTEM_PROCESSOR_LC MATCHES "x86_64" OR
@@ -158,6 +155,12 @@ elseif(CMAKE_SYSTEM_PROCESSOR STREQUAL "ppc64" AND BITS EQUAL 32)
 else()
 	set(CPU_TYPE ${CMAKE_SYSTEM_PROCESSOR_LC})
 endif()
+if(CMAKE_OSX_ARCHITECTURES MATCHES "x86_64" OR
+	CMAKE_OSX_ARCHITECTURES MATCHES "arm64" OR
+	CMAKE_OSX_ARCHITECTURES MATCHES "i386" OR
+	CMAKE_OSX_ARCHITECTURES MATCHES "ppc")
+	set(CPU_TYPE ${CMAKE_OSX_ARCHITECTURES})
+endif()
 message(STATUS "${BITS}-bit build (${CPU_TYPE})")
 include(cmakescripts/FindTurboJPEG.cmake)