[oe] PARALLEL_MAKE

[Frans Meulenbroeks]

I'm not sure how PARALLEL_MAKE is supposed to work, but I noticed that
often there is a problem because with it a package on which there is a
dependency is build in parallel. Since there is a dependency in a lot
of cases the underlying package fails.

A typical scenario:
a package X depends on perl-native, typically they start to build in
parallel but perl-native does take much longer than X. X requires
perl-native to complete and fails.

Parallelism within a task (e.g. running two compiles in parallel would work).
Parallelism between tasks is tricky although some of them can always
be parallelized (e.g. downloading, unpacking and patching).

Frans