ninja: Add a friendlier error message if no prebuilt binary is found.

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

[M-A Ruel, 2012/12/11 18:45:06]

I only meant to have "  cat << EOF" and the rest not indented. I don't mind
much.

+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 v1.0.0
+  ./ninja/bootstrap.py
+Then add ~/ninja/ to your PATH.
+EOF
+}
+
 if [ "${OS}" = "Linux" ]; then
   machine=$(getconf LONG_BIT)
   if [[ "$machine" = "64" ]]; then
     exec "${THIS_DIR}/ninja-linux64" "$@"
   elif [[ "$machine" = "32" ]]; then
     exec "${THIS_DIR}/ninja-linux32" "$@"
   else
-    echo Unknown architecture \($machine\) -- unable to run ninja.
+    echo "Unknown architecture ${machine}."
+    print_help
     exit 1
   fi
 elif [ "${OS}" = "Darwin" ]; then
   exec "${THIS_DIR}/ninja-mac" "$@"
 elif [[ ${OS} == CYGWIN* ]]; then
   exec cmd.exe /c `cygpath -t windows $0`.exe "$@"
 elif [[ ${OS} == MINGW32* ]]; then
   cmd.exe //c $0.exe "$@"
 else
   echo "Unsupported OS ${OS}"
+  print_help
   exit 1
 fi