dev-lang/ghc: fix weak symbol loading and limit maximum parallel jobs by 4 tasks

Gentoo-bug: http://bugs.gentoo.org/456386
Gentoo-bug: http://bugs.gentoo.org/452442
http://ghc.haskell.org/trac/ghc/ticket/3333

Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
dev-lang/ghc: added libc_nonshared.a to ghc-prim (first loaded ghci library)

We stuff all the 'libc_nonshared.a' symbols to make them forcefully defined
exactly one for each ghci load.

Gentoo-bug: http://bugs.gentoo.org/452442
Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>