galculator: pull fix pending upstream inclusion for -fno-common toolchains

Without the change build fails on upstream gcc-10 as:

ld: galculator-config_file.o:src/config_file.c:42:
multiple definition of `prefs'; galculator-main.o:src/main.c:52: first defined here

pkgs/applications/misc/galculator/default.nix

···
-{ lib, stdenv, fetchFromGitHub
+{ lib, stdenv, fetchFromGitHub, fetchpatch
 , autoreconfHook, intltool
 , gtk, pkg-config, flex }:
 
···
     rev = "v${version}";
     sha256 = "0q0hb62f266709ncyq96bpx4a40a1i6dc5869byvd7x285sx1c2w";
   };
+
+  patches = [
+    # Pul patch pending upstream inclusion for -fno-common toolchain support:
+    #   https://github.com/galculator/galculator/pull/45
+    (fetchpatch {
+      name = "fno-common.patch";
+      url = "https://github.com/galculator/galculator/commit/501a9e3feeb2e56889c0ff98ab6d0ab20348ccd6.patch";
+      sha256 = "08c9d2b49a1mizgk7v37dp8r96x389zc13mzv4dcy16x448lhp67";
+    })
+  ];
 
   nativeBuildInputs = [ autoreconfHook intltool pkg-config ];
   buildInputs = [ gtk flex ];