Remove _smp_mflags override on ppc64le

Using a fixed -j argument is pretty dubious and may have the
opposite of the desired effect. E.g. on a recent copr build I
see ppc64le having 5 cpus, so this actually increases the level
of parallelism (and oversubscribes...) rather than decreasing.

I don't think we have evidence that this particular workaround is
still needed, so drop it.

globals.spec.inc

@@ -105,12 +105,6 @@
 %global pkg_includedir %{install_prefix}/include
 %endif
 
-%ifarch ppc64le
-# Too many threads on ppc64 systems causes OOM errors.
-# TODO(kkleine): Is this really needed when building together with llvm?
-%global _smp_mflags -j8
-%endif
-
 #endregion
 
 #region COMPILER-RT globals