debug: Don't halt out of reset. It's unrealistic. Use a program which loops (actually it just gets an exception anyway).

I've added an additional linker relaxation that relaxes two instruction
pc-relative sequences to one instruction gp relative sequences when
possible.  This sequence now optimizes the initial gp generation to

  mv gp, gp

which is obviously bogus.  The fix is to disable relaxations when
setting up gp, preventing the linker from relaxing away this setup code.

This changed a while ago in binutils.

spike passes the download test, but needs a 15 minute timeout. That's
too ridiculous to put in here, but 60s is reasonable.