Fix ninja wrapper script on non-x86 linux.

ninja

 #!/bin/bash
 
 # Copyright (c) 2012 Google Inc. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 OS="$(uname -s)"
 THIS_DIR="$(dirname "${0}")"
 
 function print_help() {
 cat <<-EOF
 No prebuilt ninja binary was found for this system.
 Try building your own binary by doing:
   cd ~
   git clone https://github.com/martine/ninja.git -b v1.4.0
   ./ninja/bootstrap.py
 Then add ~/ninja/ to your PATH.
 EOF
 }
 
 case "$OS" in
   Linux)
-    MACHINE=$(getconf LONG_BIT)
+    MACHINE=$(uname -m)
     case "$MACHINE" in
-      32|64)  exec "${THIS_DIR}/ninja-linux${MACHINE}" "$@";;
-      *)      echo Unknown architecture \($MACHINE\) -- unable to run ninja.
-              print_help
-              exit 1;;
+      i?86|x86_64)
+        LONG_BIT=$(getconf LONG_BIT)
+        # We know we are on x86 but we need to use getconf to determine
+        # bittage of the userspace install (e.g. when runing 32-bit userspace
+        # on x86_64 kernel)
+        exec "${THIS_DIR}/ninja-linux${LONG_BIT}" "$@";;
+      *)
+        echo Unknown architecture \($MACHINE\) -- unable to run ninja.
+        print_help
+        exit 1;;
     esac
     ;;
   Darwin)    exec "${THIS_DIR}/ninja-mac" "$@";;
   CYGWIN*)   exec cmd.exe /c $(cygpath -t windows $0).exe "$@";;
   MINGW32*)  cmd.exe //c $0.exe "$@";;
   *)         echo "Unsupported OS ${OS}"
              print_help
              exit 1;;
 esac