Fixed a problem where the Xcode build put lldb's __init__.py in the wrong place.

Most of the time CONFIGURATION_BUILD_DIR and BUILT_PRODUCTS_DIR are the same,
but they are different in 'xcodebuild install' situations.  The file needs to be
put into BUILT_PRODUCTS_DIR or lldb's Python interface doesn't work when lldb is
built using 'xcodebuild install'.

llvm-svn: 257653