This fixes an issue were some LibDebug objects (for example,
Dwarf::CompilationUnit) held a reference to their parent
Dwarf::DwarfInfo object, which was constructed on the stack and later
moved to the heap.
SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
