Parse LLVM's Targets.def file automatically to get all available targets - '-J{PATH_TO_Targets.def}' *must* be passed to {r}dmd for this to work, e.g. '-J/usr/include/llvm/Config' for a common LLVM Linux installation; can be disabled via version identifier 'LLVM_NO_TARGETS_DEF', in which case available targets must be specified manually via their respective version identifiers (-> 'LLVM_TARGET_{TargetName}').