jfsutils: add -fcommon workaround

Workaround build failure on -fno-common toolchains like upstream
gcc-10. Otherwise build fails as:

    ld: extract.o:/build/jfsutils-1.1.15/fscklog/extract.c:67: multiple definition of
      `xchklog_buffer'; display.o:/build/jfsutils-1.1.15/fscklog/display.c:57: first defined here

pkgs/tools/filesystems/jfsutils/default.nix

@@ -25,6 +25,12 @@ stdenv.mkDerivation rec {
   nativeBuildInputs = [ autoreconfHook ];
   buildInputs = [ libuuid ];
 
+  # Workaround build failure on -fno-common toolchains like upstream
+  # gcc-10. Otherwise build fails as:
+  #     ld: extract.o:/build/jfsutils-1.1.15/fscklog/extract.c:67: multiple definition of
+  #       `xchklog_buffer'; display.o:/build/jfsutils-1.1.15/fscklog/display.c:57: first defined here
+  NIX_CFLAGS_COMPILE = "-fcommon";
+
   meta = with lib; {
     description = "IBM JFS utilities";
     homepage = "http://jfs.sourceforge.net";