Attempt to add with overflow in GVN when building chrono-tz

[saethlin]

https://github.com/chronotope/chrono-tz on commit 97d1680189e61fbd66fcb1c52f6d51b55389919e

RUSTFLAGS="-Zinline-mir -Zmir-opt-level=1 -Zmir-enable-passes=+GVN -Zcross-crate-inline-threshold=yes -Copt-level=1" cargo +master-stage1 build

Where master-stage1 is a toolchain build with debug assertions.

   Compiling chrono-tz v0.8.4 (/home/ben/chrono-tz/chrono-tz)
thread 'rustc' panicked at compiler/rustc_mir_transform/src/gvn.rs:650:37:
attempt to add with overflow
stack backtrace:

rustc-ice-2023-12-16T04_53_09-27142.txt