Pass target triplet to clang compiler.

Hey there. I found that I needed to add the target to clang arguments in order to get it working. Otherwise I would get an error: "error: unknown target CPU 'armv7-a'" when compiling for arm. I checked the output of ndk-build and it includes the target parameter. This is for llvm-3.3 on ndk r9c. I am on Mac OS X 10.9.2.