rts: Limit maximum backtrace depth
rts: Limit maximum backtrace depth

This prevents us from entering an infinite loop in the event of a
hitting bad unwinding information.

(cherry picked from commit 350ffc3e4c6b3aefd6ae621991564cc28f585d46)

GaloisInc/halvm-ghc,GaloisInc/halvm-ghc,GaloisInc/halvm-ghc,GaloisInc/halvm-ghc,GaloisInc/halvm-ghc,GaloisInc/halvm-ghc,GaloisInc/halvm-ghc