Summary:
This patch set fixes two issues in linker_unload test case
on Solaris/i386 platform. First there is an issue in linker_unload.c
which causes warning to be emitted about _FILE_OFFSET_BITS redefined.
This is solved by including ghcconfig.h as a first header file.
Another issue is that on Solaris and its builders we use to configure
ghc with --with-gmp-libraries=/usr/lib and this causes issue with
test case Makefile's logic. It attempts to start linker_unload
and pass it HSinteger-gmp library for unload, but the library
name is prefixed with two directories names. The first is of
ghc's integer-gmp/build itself and another is the directory name
passed to --with-gmp-libraries= configure parameter. In case
of Solaris this is /usr/lib. The testcase then fails on unloading
integer-gmp/build directory thinking that this is a library to unload.
This issue is solved by cuting the first library name from the list
and using this for unloading the HSinteger-gmp library.

Test Plan: validate

Reviewers: ezyang, austin

Reviewed By: ezyang, austin

Subscribers: phaskell, simonmar, relrod, ezyang, carter

Differential Revision: https://phabricator.haskell.org/D110