bionic: rename aarch64 target to arm64

Rename aarch64 build targets to arm64.  The gcc toolchain is still
aarch64.

Change-Id: Ia92d8a50824e5329cf00fd6f4f92eae112b7f3a3
diff --git a/libc/tools/bionic_utils.py b/libc/tools/bionic_utils.py
index 39dc76a..88ddd55 100644
--- a/libc/tools/bionic_utils.py
+++ b/libc/tools/bionic_utils.py
@@ -2,7 +2,7 @@
 
 import sys, os, commands, string
 
-all_arches = [ "aarch64", "arm", "mips", "x86", "x86_64" ]
+all_arches = [ "arm", "arm64", "mips", "x86", "x86_64" ]
 
 # basic debugging trace support
 # call D_setlevel to set the verbosity level