mold: update to 2.2.0.

New features:

- We now use BLAKE3 as a cryptographic hash function instead of SHA256.
  This change has made --build-id a few percent faster. libssl is no longer
  a build dependency.
- mold is now a few percent faster than the previous version due to an
  optimization of string merging code path.
- mold now emits slightly optimized code for thread-local variable accesses.
- [RISC-V] mold now supports TLSDESC relocations. TLSDESC is a new mechanism
  for faster thread-local variable access. We (@ishitatsuyuki) actually led
  the effort to ratify the specification (riscv-non-isa/riscv-elf-psabi-doc#373)
  and implement it to compiler toolchain including GCC, GNU binutils and,
  of course, mold.

Bug fixes and compatibility improvements:

- mold no longer marks an as-needed .so as "needed" if the .so file is not
  directly used by the output file. Previously, mold marked a .so file as
  "needed" if the .so file was used by another "needed" .so file.
- [PPC64] --execute-only now works on 64-bit PowerPC.

(fcambus)