Remove LLVM/-fPIC check in DynFlags

When the LLVM backend was first implemented the implementation did not support -fPIC or -dynamic. Support for this was added in 60873542, which merely added the appropriate -relocation-model flag to the opt command line when compiling with -fPIC. However, the error message in DynFlags.makeDynFlagsConsistent remains for all but a select few platforms,

 | hscTarget dflags == HscLlvm &&
   not ((arch == ArchX86_64) && (os == OSLinux || os == OSDarwin || os == OSFreeBSD)) &&
   not ((isARM arch) && (os == OSLinux)) &&
   (gopt Opt_PIC dflags || WayDyn `elem` ways dflags)
    = if cGhcWithNativeCodeGen == "YES"
      then let dflags' = dflags { hscTarget = HscAsm }
               warn = "Using native code generator rather than LLVM, as LLVM is incompatible with -fPIC and -dynamic on this platform"
           in loop dflags' warn
      else throwGhcException $ CmdLineError "Can't use -fPIC or -dynamic on this platform"

Is this still necessary? If so, why? If not, we should remove it.

Trac metadata

Trac field	Value
Version	8.0.1
Type	Task
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler (LLVM)
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