Use a script for creating the clang++ executable.

The previous method used the DESTDIR environment variable at configure
time, but sometimes it is only available at install time. See PR8397.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@116689 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed