Broken build: 32-bit FreeBSD, SmartOS, Solaris

[Páli Gábor János]

Hello there,

Looks one of the recent commits broke the x86 builds on multiple
platforms [1][2][3].  The common error message basically is as
follows:

rts/Linker.c: In function 'mkOc':
rts/Linker.c:2372:6:
     error: 'ObjectCode' has no member named 'symbol_extras'

Please fix it!

Note that the x86_64 counterparts of the affected builders completed
their builds fine -- except for Solaris, but that has been broken
already for a long time (relatively).

[1] http://haskell.inf.elte.hu/builders/smartos-x86-head/144/10.html
[2] http://haskell.inf.elte.hu/builders/freebsd-i386-head/403/10.html
[3] http://haskell.inf.elte.hu/builders/solaris-x86-head/191/10.html