gcc8: made the remove-selftests patch more robust, removed old hash

pkgs/development/compilers/gcc/8/default.nix

@@ -60,8 +60,8 @@ let version = "8.1.0";
          optional (targetPlatform != hostPlatform) ../libstdc++-target.patch
       ++ optional noSysDirs ../no-sys-dirs.patch
       /* ++ optional (hostPlatform != buildPlatform) (fetchpatch { # XXX: Refine when this should be applied
-        url = "https://git.busybox.net/buildroot/plain/package/gcc/7.1.0/0900-remove-selftests.patch?id=11271540bfe6adafbc133caf6b5b902a816f5f02";
-        sha256 = "0mrvxsdwip2p3l17dscpc1x8vhdsciqw1z5q9i6p5g9yg1cqnmgs";
+        url = "https://git.busybox.net/buildroot/plain/package/gcc/${version}/0900-remove-selftests.patch?id=11271540bfe6adafbc133caf6b5b902a816f5f02";
+        sha256 = ""; # TODO: uncomment and check hash when available.
       }) */
       ++ optional langFortran ../gfortran-driving.patch;