--- a/gmp/gnatcoll_gmp.gpr	2018-06-18 21:48:15.289991113 +0200
+++ b/gmp/gnatcoll_gmp.gpr	2018-06-18 21:48:46.869507399 +0200
@@ -65,7 +65,7 @@
             for Switches ("Ada") use ("-O2", "-gnatn", "-gnatwaCJ");
             for Switches ("C") use ("-O2", "-Wunreachable-code");
       end case;
-
+      for Driver ("C") use External ("GCC", "gcc");
    end Compiler;
 
    package Binder is