Do not emit .eh_frame section if using -Cpanic=abort

[antoyo]

No description provided.

[bjorn3]

.eh_frame is necessary once exceptions reaching into panic=abort rust code starts to abort the program rather than being UB.

[antoyo]

@bjorn3: This is necessary for Rust for Linux.
How do you suggest we handle this?

[bjorn3]

It may be that this change is fine and once unwinding into panic=abort rust code will abort the presence of the landingpad will cause .eh_frame to be emitted by both cg_llvm and cg_gcc. When that happens whatever solution is chosen for cg_llvm may work for cg_gcc too.

[antoyo]

@bjorn3: Do you think this should instead be set/unset depending on the value of -Cforce-unwind-tables?