v0 symbol mangling breaks proper grouping of duplicate copies

[vorporeal]

When enabling v0 symbol mangling (e.g.: by setting rustflags = "-Csymbol-mangling-version=v0" in the [build] section of the cargo config file), most duplicate copies of a function end up as their own single-copy entry in the output instead of being properly grouped.

Perhaps cargo-llvm-lines should force the symbol mangling to legacy to ensure proper behavior for projects that normally use v0?