Log Message:
mold: update to 2.0.0.

Mold 2.0.0 is a new major release of our high-speed linker. With this
release, we've transitioned our license from AGPL to MIT, aiming to expand
the user base of our linker. This was not an easy decision, as those who
have been following our progress know that we've been attempting to monetize
our product through an AGPL/commercial license dual-licensing scheme.
Unfortunately, this approach didn't meet our expectations. The license
change represents our acceptance of this reality. We don't want to persist
with a strategy that didn't work well.

In addition to the license change, here is a list of updates we have made
in this release:

- Previously, mold could not produce an object file with more than 65520
  sections using the --relocatable option. Now the bug has been fixed.
- mold now interprets -undefined as a synonym for --undefined instead of
  -u ndefined. This seems inconsistent, as -ufoo is generally treated as
  -u foo (which is an alias for --undefined foo), but this is the behavior
  of the GNU linkers and LLVM lld, so we prioritize compatibility over
  consistency.
- -nopie is now handled as a synonym for --no-pie.
- [RISC-V] R_RISCV_SET_ULEB128 and R_RISCV_SUB_ULEB128 relocation types are
  now supported.
- [PPC64] R_PPC64_REL32 relocation type is now supported.