gcc8: 8.3.0 -> 8.4.0

https://gcc.gnu.org/legacy-ml/gcc/2020-03/msg00042.html

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

@@ -43,7 +43,7 @@ with stdenv.lib;
 with builtins;
 
 let majorVersion = "8";
-    version = "${majorVersion}.3.0";
+    version = "${majorVersion}.4.0";
 
     inherit (stdenv) buildPlatform hostPlatform targetPlatform;
 
@@ -77,7 +77,7 @@ stdenv.mkDerivation ({
 
   src = fetchurl {
     url = "mirror://gcc/releases/gcc-${version}/gcc-${version}.tar.xz";
-    sha256 = "0b3xv411xhlnjmin2979nxcbnidgvzqdf4nbhix99x60dkzavfk4";
+    sha256 = "1m1d3gfix56w4aq8myazzfffkl8bqcrx4jhhapnjf7qfs596w2p3";
   };
 
   inherit patches;