* Invoke testing on linux requires libffi

packages/rtl-objpas/tests/testrunner.rtlobjpas.pp

@@ -4,8 +4,12 @@
 program testrunner.rtlobjpas;
 
 {$mode objfpc}{$H+}
+
 { Invoke needs a function call manager }
-{.$define useffi}
+{$ifdef linux}
+{$define useffi}
+{$endif}
+
 {$if defined(CPUX64) and defined(WINDOWS)}
 {$define testinvoke}
 {$define testimpl}