system_check.cmake: fix arch detection for Darwin PowerPC

cmake/system_check.cmake

@@ -38,7 +38,7 @@ if(CMAKE_CL_64 OR MINGW64)
   endif()
 elseif(MINGW OR (MSVC AND NOT CMAKE_CROSSCOMPILING))
   set(X86 1)
-elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "ppc.*|power.*|Power.*")
+elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "ppc.*|power.*|Power.*" OR (CMAKE_SYSTEM_NAME MATCHES "Darwin" AND CMAKE_OSX_ARCHITECTURES MATCHES "ppc.*"))
   set(POWER 1)
 elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "mips64.*")
   set(MIPS64 1)
@@ -109,7 +109,7 @@ else()
 endif ()
 
 if (NOT BINARY)
-  if (X86_64 OR ARM64 OR POWER OR MIPS64 OR LOONGARCH64 OR RISCV64)
+  if (X86_64 OR ARM64 OR MIPS64 OR LOONGARCH64 OR RISCV64 OR (POWER AND NOT (CMAKE_OSX_ARCHITECTURES STREQUAL "ppc")))
     set(BINARY 64)
   else ()
     set(BINARY 32)