gcc10: fix cross-compilation from aarch64-darwin host

Without this patch, linking when cross-compiling fails:

    Undefined symbols for architecture arm64:
      "_host_hooks", referenced from:
          gt_pch_save(__sFILE*) in libbackend.a(ggc-common.o)
          gt_pch_restore(__sFILE*) in libbackend.a(ggc-common.o)
          toplev::main(int, char**) in libbackend.a(toplev.o)
    ld: symbol(s) not found for architecture arm64

pkgs/development/compilers/gcc/10/default.nix

@@ -71,7 +71,12 @@ let majorVersion = "10";
       # Obtain latest patch with ../update-mcfgthread-patches.sh
       ++ optional (!crossStageStatic && targetPlatform.isMinGW) ./Added-mcf-thread-model-support-from-mcfgthread.patch
 
-      ++ [ ../libsanitizer-no-cyclades.patch ];
+      ++ [ ../libsanitizer-no-cyclades.patch ]
+
+      ++ optional (buildPlatform.system == "aarch64-darwin" && targetPlatform != buildPlatform) (fetchpatch {
+        url = "https://raw.githubusercontent.com/richard-vd/musl-cross-make/5e9e87f06fc3220e102c29d3413fbbffa456fcd6/patches/gcc-${version}/0008-darwin-aarch64-self-host-driver.patch";
+        sha256 = "sha256-XtykrPd5h/tsnjY1wGjzSOJ+AyyNLsfnjuOZ5Ryq9vA=";
+      });
 
     /* Cross-gcc settings (build == host != target) */
     crossMingw = targetPlatform != hostPlatform && targetPlatform.libc == "msvcrt";