enable 6 arg version of mmap

libc/sysdeps/linux/alpha/bits/uClibc_arch_features.h

@@ -9,7 +9,7 @@
 #define __UCLIBC_ABORT_INSTRUCTION__ "call_pal 0"
 
 /* can your target use syscall6() for mmap ? */
-#undef __UCLIBC_MMAP_HAS_6_ARGS__
+#define __UCLIBC_MMAP_HAS_6_ARGS__
 
 /* does your target use syscall4() for truncate64 ? (32bit arches only) */
 #undef __UCLIBC_TRUNCATE64_HAS_4_ARGS__