OS_AIX=$(shell expr "$(UNAME)" : '.*AIX.*')
OS_SUNOS=$(shell expr "$(UNAME)" : '.*SunOS.*')
OS_DARWIN=$(shell expr "$(UNAME)" : '.*Darwin.*')
-OS_DARWIN64=$(shell expr "$(DARWIN_LIBC)" : '.*x86_64.*')
+ifneq ($(OS_DARWIN),0)
+ OS_DARWIN64=$(shell expr "$(DARWIN_LIBC)" : '.*x86_64.*')
+else
+ OS_DARWIN64=0
+endif
OS_CYGWIN=$(shell expr "$(UNAME)" : '.*CYGWIN.*')
OS_LINUX=$(shell expr "$(UNAME)" : '.*Linux.*')
OS_LINUX64=$(shell expr "$(UNAME_A)" : '.*Linux.*x86_64.*')