They were using a fixed offset of pc+2, but since the instructions can
be multiple bytes long (leb128 encoded), it should be using *len.

Drive-by fix to add missing instructions to wasm-module-builder.js.

Bug: chromium:1185323,chromium:1185492
Change-Id: I12f396cc2969ecc284aba35b94b1bc5640f12277
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2745977
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#73308}