CI failure on FreeBSD

[bjorn3]

https://cirrus-ci.com/task/6508023653335040

Likely caused by c615e92 which started running more tests for regex.

     Running unittests src/lib.rs (build/regex/x86_64-unknown-freebsd/debug/deps/regex_syntax-a9c23066f2c22e21)
running 324 tests
.....................................F.................................................. 88/324
........................................................................................ 176/324
........................................................................................ 264/324
..........F.................................................
failures:
---- ast::tests::no_stack_overflow_on_drop stdout ----
---- ast::tests::no_stack_overflow_on_drop stderr ----
Unexpected error: child process exited with signal 11
---- hir::tests::no_stack_overflow_on_drop stdout ----
---- hir::tests::no_stack_overflow_on_drop stderr ----
Unexpected error: child process exited with signal 11
failures:
    ast::tests::no_stack_overflow_on_drop
    hir::tests::no_stack_overflow_on_drop
test result: FAILED. 322 passed; 2 failed; 0 ignored; 0 measured; 0 filtered out; finished in 2.43s
error: test failed, to rerun pass `-p regex-syntax --lib`

[bjorn3]

These tests are meant to check that drop implementations run in constant space. I guess slightly more space was used on FreeBSD than expected by these tests.

[bjorn3]

This also happens with cg_llvm. Opened rust-lang/regex#967.