Refactor snapshot build (#2825)

Instead of using core/snapshot_creator.rs, instead two crates are
introduced which allow building the snapshot during build.rs.

Rollup is removed and replaced with our own bundler. This removes
the Node build dependency. Modules in //js now use Deno-style imports
with file extensions, rather than Node style extensionless imports.

This improves incremental build time when changes are made to //js files
by about 40 seconds.

1 files changed, 4 insertions, 4 deletions

diff --git a/js/buffer.ts b/js/buffer.ts
index 9525e6954..dc73b7e60 100644
--- a/js/buffer.ts
+++ b/js/buffer.ts
@@ -4,10 +4,10 @@
 // Copyright 2009 The Go Authors. All rights reserved. BSD license.
 // https://github.com/golang/go/blob/master/LICENSE
 
-import { Reader, Writer, EOF, SyncReader, SyncWriter } from "./io";
-import { assert } from "./util";
-import { TextDecoder } from "./text_encoding";
-import { DenoError, ErrorKind } from "./errors";
+import { Reader, Writer, EOF, SyncReader, SyncWriter } from "./io.ts";
+import { assert } from "./util.ts";
+import { TextDecoder } from "./text_encoding.ts";
+import { DenoError, ErrorKind } from "./errors.ts";
 
 // MIN_READ is the minimum ArrayBuffer size passed to a read call by
 // buffer.ReadFrom. As long as the Buffer has at least MIN_READ bytes beyond