This patch replaces LLVM_ATTRIBUTE_UNUSED with [[maybe_unused]],
introduced as part of C++17.

https://github.com/codespell-project/codespell
```bash
codespell bolt --skip="*.yaml,Maintainers.txt" --write-changes \
    --ignore-words-list=acount,alledges,ans,archtype,defin,iself,mis,mmaped,othere,outweight,vas
```

This patch fixes a bug in BOLT's debug line emission where functions
that belong to multiple compilation units (such as inline functions in
header files) were not handled correctly. Previously, BOLT incorrectly
assumed that a binary function could belong to only one compilation
unit, leading to incomplete or incorrect debug line information.

### **Problem**

When a function appears in multiple compilation units (common scenarios
include):

*   Template instantiated functions
* Inline functions defined in header files included by multiple source
files

BOLT would only emit debug line information for one compilation unit,
losing debug information for other CUs where the function was compiled.
This resulted in incomplete debugging information and could cause
debuggers to fail to set breakpoints or show incorrect source locations.

### **Root Cause**

The issue was in BOLT's assumption that each binary function maps to
exactly one compilation unit. However, when the same function (e.g., an
inline function from a header) is compiled into multiple object files,
it legitimately belongs to multiple CUs in the final binary.

While I'm at it, this patch removes GetExecutablePath, which becomes
unused after removing the sole use.

Fix DebugStrOffsetsWriter so updateAddressMap can't be called after it
is finalized.

Refactors address writers to create an instance for each CU and its DWO
CU.

Cleanup buffer initialization for DWO range writer instances to remove
empty buffer at the beginning.

Removes unnecessary SectionOffset variable from DebugData.

Refactors legacy ranges writers to create a writer for each instance of
a DWO file.

We now write out everything into .debug_ranges after the all the DWO
files are processed. This also changes the order that ranges is written
out in, as before we wrote out while in the main CU processing loop and
we now iterate through the CU buckets created by partitionCUs, after the
main processing loop.