llvm-exegesis: Set the module triple and ABI-aware DataLayout (#228447)
The module used to assemble snippets only had a DataLayout set, which
was computed without the target ABI. Set the target triple on the
module, synthesize the "target-abi" module flag from the
TargetMachine's ABI option, and compute the DataLayout from it.
Without the ABI, a TargetMachine with a non-default ABI would hit the
incompatible DataLayout error when creating the MachineFunction.
Co-Authored-By: Claude <noreply@anthropic.com>