Warn and disable dynamic_arch when not supported on the architecture

cmake/system.cmake

@@ -199,12 +199,15 @@ if (NEED_PIC)
   endif()
 endif ()
 
-if (X86 OR X86_64 OR ARM64 OR PPC)
-  if (DYNAMIC_ARCH)
+if (DYNAMIC_ARCH)
+  if (X86 OR X86_64 OR ARM64 OR PPC)
     set(CCOMMON_OPT "${CCOMMON_OPT} -DDYNAMIC_ARCH")
     if (DYNAMIC_OLDER)
       set(CCOMMON_OPT "${CCOMMON_OPT} -DDYNAMIC_OLDER")
     endif ()
+  else ()
+    unset (DYNAMIC_ARCH)
+    message (STATUS "DYNAMIC_ARCH is not supported on the target architecture, removing")
   endif ()
 endif ()