Adding default_exe_manifest to two binaries

gn builds are missing Windows manifests for d8.exe and
mksnapshot.exe. These manifests are necessary in order to get
predictable behavior on Windows.

LOG=N
BUG=602505

Review-Url: https://codereview.chromium.org/1941433002
Cr-Commit-Position: refs/heads/master@{#35943}

BUILD.gn

@@ -2037,6 +2037,7 @@ if (current_toolchain == snapshot_toolchain) {
       ":v8_libplatform",
       ":v8_nosnapshot",
       "//build/config/sanitizers:deps",
+      "//build/win:default_exe_manifest",
     ]
   }
 }
@@ -2106,6 +2107,7 @@ if ((current_toolchain == host_toolchain && v8_toolset_for_d8 == "host") ||
       ":v8",
       ":v8_libplatform",
       "//build/config/sanitizers:deps",
+      "//build/win:default_exe_manifest",
     ]
 
     # TODO(jochen): Add support for vtunejit.