autofdo needs libprotofbuf-dev

[algr]

libprotobuf-dev should be added to the apt package dependencies in the README. protobuf-compiler is listed, but this is not enough. Without libprotobuf-dev, cmake will fail:

  Could NOT find Protobuf (missing: Protobuf_LIBRARIES Protobuf_INCLUDE_DIR)
Call Stack (most recent call first):
  /usr/local/lib/python3.6/dist-packages/cmake/data/share/cmake-3.21/Modules/FindPackageHandleStandardArgs.cmake:594 (_FPHSA_FAILURE_MESSAGE)
  /usr/local/lib/python3.6/dist-packages/cmake/data/share/cmake-3.21/Modules/FindProtobuf.cmake:650 (FIND_PACKAGE_HANDLE_STANDARD_ARGS)
  CMakeLists.txt:22 (find_package)
  CMakeLists.txt:548 (config_without_llvm)