* We always need use_sigaltstack=0 because Ruby registers sigaltstack
handlers
* We also need to disable leak detection (unless RUBY_FREE_AT_EXIT is
set - I might experiment later with automatically enabling leak
detection if RUBY_FREE_AT_EXIT is set).
Burning it into the built ruby binary in this way avoids people needing
to remember to start their Ruby program with these flags all the time.
We also need a small fix in mkmf to make sure that test programs also
don't have leak detection enabled (this is never desirable)
[Bug #20256]
1d467f2255