clang-tidy: need way to pass additional tidy-specific compiler options

The value of CMAKE_CXX_CLANG_TIDY is a ;-list that is converted by this code to a clang-tidy command line of the following form:

${CMAKE_CXX_CLANG_TIDY} '/path/to/src.cxx' -- ${original_compiler_command}

The value of CMAKE_CXX_CLANG_TIDY is expected to contain the clang-tidy command along with options to it. However, the tool does not support passing clang options directly. Instead they need to be added after the original compiler command. We will need a new way to specify such options.