Add AArch64 build support

Enhance package-avrdude.bash to know about AArch64.

libelf's config.guess is too old to know about AArch64. Add a patch to
replace it with the version from libusb.

Author: nvswarren

libelf-0.8.13-patches/01-config.guess.patch

@@ -28,6 +28,7 @@ fi
 tar xfv libelf-0.8.13.tar.gz
 
 cd libelf-0.8.13
+for p in ../libelf-0.8.13-patches/*.patch; do echo Applying $p; patch -p0 < $p; done
 CONFARGS="--prefix=$PREFIX --disable-shared"
 if [[ $CROSS_COMPILE != "" ]] ; then
   CONFARGS="$CONFARGS --host=$CROSS_COMPILE_HOST"

libelf-0.8.13.build.bash

@@ -37,6 +37,8 @@ elif [[ $OS == "GNU/Linux" ]] ; then
     OUTPUT_TAG=i686-pc-linux-gnu
   elif [[ $MACHINE == "armv7l" ]] ; then
     OUTPUT_TAG=armhf-pc-linux-gnu
+  elif [[ $MACHINE == "aarch64" ]] ; then
+    OUTPUT_TAG=aarch64-pc-linux-gnu
   else
     echo Linux Machine not supported: $MACHINE
     exit 1