`perf2bolt` and `llvm-boltdiff` are now not separate targets but just
symlinks to `llvm-bolt` created when you install `llvm-bolt` itself so
when you try to build it ninja reports there are no targets for both of
them
Updates the Dockerfile to use Ubuntu 24.04 due to CMake wanting a newer
version. Can be tested by trying to build the Docker image currently in
main and then try building the Docker image in this PR.