Shared lib support for Linux

[Iain Buclaw]

== Quote from Long Chang (changlong at jkys.info)'s article
> Hello ,
> The DMD will support shared lib for linux in future,  But I wan't to
> know when this can be completed .
> I am try use GDC build libgdruntime.a with -fPIC,  and catch some
> error I can't fix it .
> for example:
> ../../../../libphobos/rt/arraybyte.d
> ../../../../libphobos/rt/arraybyte.d: In function
> ‘_arraySliceExpAddSliceAssign_g’:
> ../../../../libphobos/rt/arraybyte.d:220: error: PIC register ‘ebx
> ’
> clobbered in ‘asm’
> If Druntime team can help GDC team fix this issue will be great .
> Kind Regards / Long Chang

Ignoring any bugs in Druntime and DMD regarding PIC code generation; GDC puts all
used registers in any given asm statement in the clobbered list. Without this, GCC
will not know of their usage, and so assumes the register(s) are free, therefore
it may decide to use them for storing other data.

Regards