In order to resolve PR25059, we're going to need to be able to generate symlinks to libraries manually, so I need this code to be reusable.
llvm-svn: 250573
In order to support building clang out-of-tree the install_symlink script needs to be installed, and it needs to be found by searching the CMAKE_MODULE_PATH.
This change renames install_symlink -> LLVMInstallSymlink so it doesn't conflict with naming from other projects, and adds searching behavior in AddLLVM.cmake
llvm-svn: 248009