Look for CMake.app when searching for cmake

[tfiala]

Summary

On OS X systems, look for /Applications/CMake.app and ~/Applications/CMake.app versions of the cmake command line binary when trying harder to find a cmake not on the system path.

[clayborg]

Looks good!

lldb/trunk/scripts/Xcode/build-llvm.py

 #!/usr/bin/env python
 
 import errno
 import hashlib
 import os
+import platform
 import subprocess
 import sys
 
 from lldbbuild import *
 
 #### SETTINGS ####
 
 def LLVM_HASH_INCLUDES_DIFFS ():
def find_cmake ():
     # Check a few more common spots.  Xcode launched from Finder 
     # will have the default environment, and may not have
     # all the normal places present.
     extra_cmake_dirs = [
         "/usr/local/bin",
         "/opt/local/bin",
         os.path.join(os.path.expanduser("~"), "bin")
     ]
+
+    if platform.system() == "Darwin":
+        # Add locations where an official CMake.app package may be installed.
+        extra_cmake_dirs.extend([
+           os.path.join(
+               os.path.expanduser("~"),
+               "Applications",
+               "CMake.app",
+               "Contents",
+               "bin"),
+           os.path.join(
+               os.sep,
+               "Applications",
+               "CMake.app",
+               "Contents",
+               "bin")])
+
     cmake_binary = find_executable_in_paths("cmake", extra_cmake_dirs)
     if cmake_binary:
         # We found it in one of the usual places.  Use that.
         return cmake_binary
 
     # We couldn't find cmake.  Tell the user what to do.
     raise Exception(
         "could not find cmake in PATH ({}) or in any of these locations ({}), "