gcc8: fix build w/glibc-2.36

Failing Hydra build: https://hydra.nixos.org/build/193370420

+1
+1
pkgs/development/compilers/gcc/8/default.nix
··· 53 53 url = "https://gcc.gnu.org/git/?p=gcc.git;a=patch;h=de31f5445b12fd9ab9969dc536d821fe6f0edad0"; 54 54 sha256 = "0sd52c898msqg7m316zp0ryyj7l326cjcn2y19dcxqp15r74qj0g"; 55 55 }) 56 + ../9/fix-struct-redefinition-on-glibc-2.36.patch 56 57 ] ++ optional (targetPlatform != hostPlatform) ../libstdc++-target.patch 57 58 ++ optional targetPlatform.isNetBSD ../libstdc++-netbsd-ctypes.patch 58 59 ++ optional noSysDirs ../no-sys-dirs.patch