Two dist-check related changes:

1. Allow DIST_CHECK_CONFIG_OPTION to specify a set of options to be passed
   to the configure script during the dist-check target. This allows things
   to be passed down on a project basis so the configure doesn't fail.

2. Use the tar | (cd ; tar ) idiom to copy files which is more flexible
   than using the cp command. THis allows us to exclude CVS .svn
   directories at source rather than stripping them out of the tar ball.

llvm-svn: 22166