the default version for llvm/clang used in the install_deps.sh script is 3.4. Since I didn't find clang-3.4 for my distribution, I tried 3.5 and 3.6. However, both of them faild building OSL 1.7.1.
Clang-3.5 requires OSL_BUILD_CPP11 to be set whereas OSL 1.7.1 does apparently not build with Clang-3.6 at all (https://github.com/imageworks/OpenShadingLanguage/issues/480).
So this patch should fix the Clang-3.5 problem and issue an error in case using a newer Clang version.