Allow compilation of rtl for i386-openbsd target with -dOLD_ASSEMBLER

(cherry picked from commit ed1bbfc950e9d94a5dd3ade718b54ab5beed3452)

rtl/i386/math.inc

@@ -179,8 +179,10 @@ const
     end;
 
 
-  {$ifdef OLD_ASSEMBLER}
-    {$define DISABLE_PIC_IN_EXP_REAL}
+  {$if not defined(FPC_PIC) or defined(OLD_ASSEMBLER)}
+    {$ifndef OPENBSD}
+      {$define DISABLE_PIC_IN_EXP_REAL}
+    {$endif ndef OPENBSD}
   {$endif}
   {$define FPC_SYSTEM_HAS_EXP}
     { exp function adapted from AMath library (C) Copyright 2009-2013 Wolfgang Ehrhardt