add TARGET_X8664 on macOS so mth_avx512helper.h builds

Author: s-u

runtime/libpgmath/lib/CMakeLists.txt

@@ -59,11 +59,11 @@ if(${CMAKE_SYSTEM_PROCESSOR} MATCHES "x86_64|AMD64" AND NOT ${LIBPGMATH_WITH_GEN
 
   elseif(${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
     set(DEFINITIONS_L1 HOST_OSX MAXCPUS=256 MAXCPUSL=8 MAXCPUSR=4 OSX OSX86
-      OSX8664 TARGET_OSX TARGET_OSX_X86 TARGET_OSX_X8664 TARGET_X86
+      OSX8664 TARGET_OSX TARGET_OSX_X86 TARGET_OSX_X8664 TARGET_X86 TARGET_X8664
       TARGET_X8664 __gnu_osx__ PG_PIC)
     set(FLAGS_L1 "-m64 -O3 -fomit-frame-pointer ")
 
-    set(DEFINITIONS_L2 OSX86 TARGET_OSX_X86 TARGET_OSX_X8664 PG_PIC)
+    set(DEFINITIONS_L2 OSX86 TARGET_OSX_X86 TARGET_OSX_X8664 TARGET_X8664 PG_PIC)
     set(FLAGS_L2 "-m64 -O3 -fomit-frame-pointer -mavx2 -mfma ")
 
     # common