Parallelize the library build process

Build process paralelized.

Times:
---------
make     1:06 -> 1:07 (no change)
make -j  0:24 -> 0:20 (slightly faster)

make clean     0:34 -> 0:35 (no change)
make clean -j  0:34 -> 0:14 (60% faster)

make stylecheck     1:43 -> 1:54 (slightly slower due to file creation)
make stylecheck -j8 1:43 -> 0:34 (Rapidly faster)