Disable parallel building

Parallel building is not well implemented in (upstream) Makefile, so it produces unpredictable results sometimes. Either some linking issues during the build, or it results in a library shared object, that looks OK, but misses some symbols, which is found late at runtime when the symbols are used by some application likned against the library.

Related: rhbz#2134397

Signed-off-by: Michael Petlan mpetlan@redhat.com