Add clang include path. (Fix building on opensuse tumbleweed) (#898)

Author: Mark Nefedov

CMakeLists.txt

@@ -155,6 +155,7 @@ if(BUILD_CLANG_PLUGIN)
     ${LLVM_PREFIX_DIR}/lib/clang/${LLVM_VERSION_MAJOR}.${LLVM_VERSION_MINOR}.${LLVM_VERSION_PATCH}/include
     ${LLVM_PREFIX_DIR}/lib/clang/${LLVM_VERSION_MAJOR}.${LLVM_VERSION_MINOR}/include
     ${LLVM_PREFIX_DIR}/lib/clang/${LLVM_VERSION_MAJOR}/include
+    ${LLVM_PREFIX_DIR}/lib64/clang/${LLVM_VERSION_MAJOR}.${LLVM_VERSION_MINOR}.${LLVM_VERSION_PATCH}/include
     DOC "Path to internal clang headers. Typically, $LLVM_INSTALL_PREFIX/include/clang/<llvm-version>/include")
 
   if(EXISTS ${FOUND_CLANG_INCLUDE_PATH})