Update snapshot scripts to understand new dir layout

src/etc/get-snapshot.py

@@ -9,7 +9,7 @@ def unpack_snapshot(snap):
   print("opening snapshot " + dl_path)
   tar = tarfile.open(dl_path)
   kernel = get_kernel()
-  for name in snapshot_files[kernel]:
+  for name in old_snapshot_files[kernel]:
     p = "rust-stage0/" + name
     fp = os.path.join("stage0", name)
     print("extracting " + fp)

src/etc/snapshot.py

@@ -16,6 +16,15 @@ download_dir_base = "dl"
 download_unpack_base = os.path.join(download_dir_base, "unpack")
 
 snapshot_files = {
+    "linux": ["rustc", "glue.o", "lib/libstd.so" ],
+    "macos": ["rustc", "glue.o", "lib/libstd.dylib" ],
+    "winnt": ["rustc.exe", "glue.o", "lib/std.dll" ]
+    }
+
+# This is a transitional list of files so that the unpacker knows to
+# use the old directory layout and the snapshotter knows to use the
+# new directory layout
+old_snapshot_files = {
     "linux": ["rustc", "glue.o", "libstd.so" ],
     "macos": ["rustc", "glue.o", "libstd.dylib" ],
     "winnt": ["rustc.exe", "glue.o", "std.dll" ]