Catch conflicting usage of ARCH in at least some BSD environments

fixes #1796

Author: martin-frbg

Makefile.system

@@ -9,6 +9,11 @@ ifndef TOPDIR
 TOPDIR = .
 endif
 
+# Catch conflicting usage of ARCH in some BSD environments
+ifeq ($(ARCH), amd64)
+override ARCH=x86_64
+endif
+
 NETLIB_LAPACK_DIR = $(TOPDIR)/lapack-netlib
 
 # Default C compiler