build: don't install rr outside x86

Package does not exist.

Fix https://github.com/cirosantilli/linux-kernel-module-cheat/issues/149

build

@@ -5,6 +5,7 @@ import copy
 import itertools
 import math
 import os
+import platform
 import re
 import subprocess
 
@@ -497,12 +498,14 @@ Which components to build. Default: qemu-buildroot
                 # Core requirements for this repo.
                 'git',
                 'moreutils', # ts
-                'rr',
                 'squashfs-tools',
                 'tmux',
                 'vinagre',
                 'wget',
             }
+            if platform.machine() == 'x86_64':
+                # https://github.com/rr-debugger/rr/issues/1373
+                apt_get_pkgs.add('rr')
             # E.g. on an ARM host, the package gcc-arm-linux-gnueabihf
             # is called just gcc.
             processor = self.env['host_arch']