workaround Solaris 11 GNU C CPP issue by using GNU C 3.4 as CPP

Summary:
Solaris 11 distributed GNU C 4.5.x is configured in a way that its
CPP is not working well while invoked from GHC. GHC runs it with
-x assembler-with-cpp and in this particular configuration GNU C CPP
does not provide any line-markers so GHC's output of errors or warnings
is confusing since it points to preprocessed file in /tmp and not
to the original Haskell file. Fortunately old GNU C 3.4.x is still
provided by the OS and when installed it'll be used automatically
as GHC CPP which is whole logic of this patch. So although we use modern
GCC as a C compiler and assembler we use old GCC as a C preprocessor.

Test Plan: validate

Reviewers: austin

Reviewed By: austin

Subscribers: phaskell, simonmar, relrod, ezyang, carter

Differential Revision: https://phabricator.haskell.org/D151