Recognize aarch64 for --enable-targets as advertised.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174288 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/autoconf/configure.ac b/autoconf/configure.ac
index 0a291c1..4ca4eb9 100644
--- a/autoconf/configure.ac
+++ b/autoconf/configure.ac
@@ -788,6 +788,7 @@
         x86_64)   TARGETS_TO_BUILD="X86 $TARGETS_TO_BUILD" ;;
         sparc)    TARGETS_TO_BUILD="Sparc $TARGETS_TO_BUILD" ;;
         powerpc)  TARGETS_TO_BUILD="PowerPC $TARGETS_TO_BUILD" ;;
+        aarch64)  TARGETS_TO_BUILD="AArch64 $TARGETS_TO_BUILD" ;;
         arm)      TARGETS_TO_BUILD="ARM $TARGETS_TO_BUILD" ;;
         mips)     TARGETS_TO_BUILD="Mips $TARGETS_TO_BUILD" ;;
         mipsel)   TARGETS_TO_BUILD="Mips $TARGETS_TO_BUILD" ;;