```cmake
set(PBM_PREFIX protobuf_mutator)
set(PBM_PATH ${CMAKE_CURRENT_BINARY_DIR}/${PBM_PREFIX}/src/${PBM_PREFIX})
set(PBM_LIB_PATH ${PBM_PATH}/src/libprotobuf-mutator.a)
set(PBM_FUZZ_LIB_PATH ${PBM_PATH}/src/libfuzzer/libprotobuf-mutator-libfuzzer.a)

ExternalProject_Add(${PBM_PREFIX}
  PREFIX ${PBM_PREFIX}
  GIT_REPOSITORY https://github.com/google/libprotobuf-mutator.git
  GIT_TAG master
  CONFIGURE_COMMAND ${CMAKE_COMMAND} -G${CMAKE_GENERATOR}
    -DCMAKE_C_COMPILER=${CMAKE_C_COMPILER}
    -DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER}
    -DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}
  BUILD_COMMAND ${CMAKE_MAKE_PROGRAM}
  BUILD_BYPRODUCTS ${PBM_LIB_PATH} ${PBM_FUZZ_LIB_PATH}
  BUILD_IN_SOURCE 1
  INSTALL_COMMAND ""
  LOG_DOWNLOAD 1
  LOG_CONFIGURE 1
  LOG_BUILD 1
  )

set(ProtobufMutator_INCLUDE_DIRS ${PBM_PATH})
set(ProtobufMutator_LIBRARIES ${PBM_FUZZ_LIB_PATH} ${PBM_LIB_PATH})
```

Fix incremental builds of the fuzzer
user
```cmake
set(PBM_PREFIX protobuf_mutator)
set(PBM_PATH ${CMAKE_CURRENT_BINARY_DIR}/${PBM_PREFIX}/src/${PBM_PREFIX})
set(PBM_LIB_PATH ${PBM_PATH}-build/src/libprotobuf-mutator.a)
set(PBM_FUZZ_LIB_PATH ${PBM_PATH}-build/src/libfuzzer/libprotobuf-mutator-libfuzzer.a)

ExternalProject_Add(${PBM_PREFIX}
  PREFIX ${PBM_PREFIX}
  GIT_REPOSITORY https://github.com/google/libprotobuf-mutator.git
  GIT_TAG master
  CMAKE_ARGS -DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}
  CMAKE_CACHE_ARGS -DCMAKE_C_COMPILER:FILEPATH=${CMAKE_C_COMPILER}
                   -DCMAKE_CXX_COMPILER:FILEPATH=${CMAKE_CXX_COMPILER}
  BUILD_BYPRODUCTS ${PBM_LIB_PATH} ${PBM_FUZZ_LIB_PATH}
  UPDATE_COMMAND ""
  INSTALL_COMMAND ""
  )

set(ProtobufMutator_INCLUDE_DIRS ${PBM_PATH})
set(ProtobufMutator_LIBRARIES ${PBM_FUZZ_LIB_PATH} ${PBM_LIB_PATH})
```
assistant