Log Message:
Changes 3.1.10:

New features and improvements:
* Added support for the -Xclang compiler option.
* Improved handling of exit code of internally executed processes.
* Zero length object files in the cache are now rejected as invalid.
* Bail out on option -gsplit-dwarf (since it produces multiple output files).
* Compiler option -fdebug-prefix-map is now ignored (not part of the hash). (The \ 
-fdebug-prefix-map option may be used in combination with CCACHE_BASEDIR to \ 
reuse results across different directories.)
* Added note in documentation that --ccache-skip currently does not mean \ 
“don’t hash the following option”.
* To enable support for precompiled headers (PCH), CCACHE_SLOPPINESS now also \ 
needs to include the new pch_defines sloppiness. This is because ccache \ 
can’t detect changes in the source code when only defined macros have been \ 
changed.
* Stale files in the internal temporary directory (<ccache_dir>/tmp) are \ 
now cleaned up if they are older than one hour.

Bug fixes:
* Fixed path canonicalization in make_relative_path() when path doesn’t exist.
* Fixed bug in common_dir_prefix_length(). This corrects the CCACHE_BASEDIR behavior.
* ccache no longer tries to create the cache directory when CCACHE_DISABLE is set.
* Fixed bug when reading manifests with a very large number of file info entries.
* Fixed problem with logging of current working directory.