https://bugs.freedesktop.org/show_bug.cgi?id=99013
--- Comment #7 from Michel Dänzer michel@daenzer.net --- (In reply to Christoph Haag from comment #6)
The build system already uses llvm-config --version which contains the revision for svn versions.
That just prints "4.0.0svn" for me, using the LLVM Git mirror.