message: Allow builder to set `GIT_COMMIT_HASH`
diff: @@ -196,12 +196,14 @@ if(${CMAKE_SYSTEM_NAME} STREQUAL "SunOS")
  set(SUN TRUE)
  endif()
  +if (NOT DEFINED GIT_COMMIT_HASH)
  execute_process(
  COMMAND git log -1 --format=%h
  WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
  RESULT_VARIABLE GIT_RESULT
  OUTPUT_VARIABLE GIT_COMMIT_HASH
  OUTPUT_STRIP_TRAILING_WHITESPACE)
  +endif()
  execute_process(
  COMMAND git describe --tags --abbrev=0
  WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
  