…unctions introduced in

spack#9199

Instead of replacing rpaths with placeholder and then checking strings, make use of the functions
relocate.is_recocatable and relocate.is_file_relocatable to decide if a package needs the allow-root option.

This fixes a problem where the placeholder path was not in the first rpath entry. This was seen in c++ libraries and binaries because the compiler was outside the spack install base path and always appears first in the rpath.

Instead of checking the first rpath entry, all rpaths have the placeholder path and the old install path (if it exists) replaced with the new install path.