Don't emit a blank line when running llvm-config --system-libs.

Summary:
Previously llvm-config --system-libs would print something like:

$ llvm-config --system-libs

-lz -ltinfo -lrt -ldl -lm

Now we don't emit blank line. Functionality is unchanged otherwise, in
particular llvm-config --libs --system-libs still emits the LLVM libraries
and the system libraries on different lines.

Reviewers: chapuni

Reviewed By: chapuni

CC: llvm-commits

Differential Revision: http://llvm-reviews.chandlerc.com/D2901