Merge pull request #310 from brson/aarch64

Fixes for rustup-setup.sh

Author: alexcrichton

rustup-setup.sh

@@ -126,12 +126,16 @@ get_architecture() {
             local _ostype="${_ostype}eabihf"
             ;;
 
+	aarch64)
+	    local _cputype=aarch64
+	    ;;
+
         x86_64 | x86-64 | x64 | amd64)
             local _cputype=x86_64
             ;;
 
         *)
-            err "unknown CPU type: $CFG_CPUTYPE"
+            err "unknown CPU type: $_cputype"
 
     esac