gcc7: fix build w/glibc-2.36

Failing Hydra build: https://hydra.nixos.org/build/193340626

pkgs/development/compilers/gcc/7/default.nix

···
           url = "https://gcc.gnu.org/git/?p=gcc.git;a=patch;h=de31f5445b12fd9ab9969dc536d821fe6f0edad0";
           sha256 = "0sd52c898msqg7m316zp0ryyj7l326cjcn2y19dcxqp15r74qj0g";
         })
+
+        ../9/fix-struct-redefinition-on-glibc-2.36.patch
       ]
       ++ optional (targetPlatform != hostPlatform) ../libstdc++-target.patch
       ++ optionals targetPlatform.isNetBSD [