mojolpm: fix buffer overflow in generated code

The code was taking the address of the string object instead of taking
the address of the underlying data that it contains. As a a consequence,
we were simply overwriting the content of the string object. Using
`data` here completely remove the confusion.

Bug: 361601756,361992470
Change-Id: I646771b98e05028501b17c80f441b52f95ed58b8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5816731
Auto-Submit: Paul Semel <paulsemel@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Commit-Queue: Paul Semel <paulsemel@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1347960}