Only the interpreter requires this currently since the stack register
doesn't match.
The JITs correctly set up their stack register and matches what the API
wants.
This is guaranteed to work. signal + rt_sigreturn is a handshake with
the kernel to return the data that the kernel wants.
Only time this doesn't align is when the guest signal handler longjumps
out of the signal handler. Which leaves a dangling entry in the
SignalFrame stack on the interpreter.
Ryan Houdek
ef3338ec0d