Add architecture mappings for FreeBSD12

Makefile.system

@@ -12,7 +12,13 @@ endif
 # Catch conflicting usage of ARCH in some BSD environments
 ifeq ($(ARCH), amd64)
 override ARCH=x86_64
-endif
+else ifeq ($(ARCH), powerpc64)
+override ARCH=power
+else ifeq (($ARCH), i386)
+override ARCH=x86
+else ifeq ($(ARCH), aarch64)
+override ARCH=arm64
+endif 
 
 NETLIB_LAPACK_DIR = $(TOPDIR)/lapack-netlib