runtime:mayMoreStackMove: TestCleanupLost failures

[gopherbot]

#!watchflakes
default <- pkg == "runtime:mayMoreStackMove" && test == "TestCleanupLost"

Issue created automatically to collect these failures.

Example (log):

=== RUN   TestCleanupLost
    mcleanup_test.go:336: expected 399 cleanups to be executed, got 400
--- FAIL: TestCleanupLost (0.01s)

— watchflakes

[gopherbot]

Found new dashboard test flakes for:

#!watchflakes
default <- pkg == "runtime:mayMoreStackMove" && test == "TestCleanupLost"

2025-09-05 15:06 gotip-darwin-arm64-longtest go@bb48272e runtime:mayMoreStackMove.TestCleanupLost (log)

=== RUN   TestCleanupLost
    mcleanup_test.go:336: expected 399 cleanups to be executed, got 400
--- FAIL: TestCleanupLost (0.01s)

— watchflakes