Test various Clang/LLVM build time optimizations

[SimeonEhrig]

• -DLLVM_OPTIMIZED_TABLEGEN=ON
• lld instead gold linker
• -DLLVM_PARALLEL_LINK_JOBS and -DLLVM_PARALLEL_COMPILE_JOBS instead Ninja parallel jobs

Thanks to @ax3l

[SimeonEhrig]

http://llvm.org/docs/GettingStarted.html#common-problems