[ccache] base_dir and -Xclang option - bug or incompleteness?

Hi, I have two copies of the same project and use base_dir option to share cache between them. And everything works fine until there are such options in command line: ... -Xclang -load -Xclang /project1/path/libFindBadConstructs.so ... The path to the libFindBadConstructs.so is slightly different:

[ccache] Buffer size for IO operations is too small

I've discovered that there is too small buffer size for IO in ccache: 16k or 10k (in hash_fd, copy_fd, copy_file). I did simple fix and run several tests (on mac osx) trying to recompile chromium. (Of course there was 100% cache hit). Results (pay your attention to sys time): 16k real 8m47.043s