This environment variable can be filled with compiler arguments which
will eventually appended to the arguments passed to
clang_parseTranslationUnit.
Sample use-case, adding clazy plugin:
$ export KDEV_CLANG_EXTRA_ARGUMENTS="-Xclang -load -Xclang ClangLazy.so
-Xclang -add-plugin -Xclang clang-lazy"
$ kdevelop