pari: unbreak on aarch64-darwin

pkgs/applications/science/math/pari/default.nix

@@ -40,7 +40,7 @@ stdenv.mkDerivation rec {
     "--with-gmp=${lib.getDev gmp}"
     "--with-readline=${lib.getDev readline}"
   ]
-  ++ lib.optional stdenv.isDarwin "--host=x86_64-darwin"
+  ++ lib.optional stdenv.isDarwin "--host=${stdenv.system}"
   ++ lib.optional withThread "--mt=pthread";
 
   preConfigure = ''
@@ -48,7 +48,7 @@ stdenv.mkDerivation rec {
   '';
 
   postConfigure = lib.optionalString stdenv.isDarwin ''
-    echo 'echo x86_64-darwin' > config/arch-osname
+    echo 'echo ${stdenv.system}' > config/arch-osname
   '';
 
   makeFlags = [ "all" ];
@@ -83,7 +83,6 @@ stdenv.mkDerivation rec {
     license = licenses.gpl2Plus;
     maintainers = with maintainers; [ ertes ] ++ teams.sage.members;
     platforms = platforms.linux ++ platforms.darwin;
-    broken = stdenv.isDarwin && stdenv.isAarch64;
     mainProgram = "gp";
   };
 }