[CP] [vm/ffi] Fix variadic arguments on MacOS Arm64

[dcharkes]

Commit(s) to merge

• c0b938c

Target

stable

Prepared changelist for beta/stable

https://dart-review.googlesource.com/c/sdk/+/369822

Issue Description

Variadic arguments on Mac Arm64 weren't working correctly due to misalingment.

What is the fix

Distinguishing stack alignment of FFI call arguments between varargs and non-varargs.

Why cherry-pick

To prevent JNIgen having to target the 3.5 master branch for Flutter/Dart.

• [cronet_http] Crash occurring on 32bit android devices since version 1.2.1 http#1213 (comment)

Risk

Small: It's a couple of lines of code CL (with many lines of code tests).

Issue link(s)

#55471

Extra Info

No response

[mit-mit]

sgtm

[athomas]

Released in 3.4.4.