Summary:
The CLANG_VERSION for svn clang versions have a svn suffix "8.0.0svn" and all the libraries have a svn suffix.
But not the in builtin include dir. It still points to
"/usr/lib/clang/8.0.0/include/cpuid.h"
without the suffix.

Extend the PATH_SUFFIXES to also looks a version without svn suffix.

BUG: 399439

Test Plan:
- install clang-svn
- execute cmake .. (for kdevelop)
-> it will fail

Reviewers: #kdevelop, kfunk

Reviewed By: #kdevelop, kfunk

Subscribers: kdevelop-devel

Tags: #kdevelop

Differential Revision: https://phabricator.kde.org/D15998