At main startup, if the ELF auxiliary vector contains a stacksize value,
use it as a hint for the minimum stacksize required by the executable.
1. Never lower the hard-limit. Once a hard-limit is lowered, then it can
never be increased (including child processes).
2. If hint exceeds hard-limit then clamp hint to hard-limit.
3. If soft-limit exceeds hint then do nothing.
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