This patch is aimed a fixing large numbers of x86_64-cloudabi failures
caused by gas selecting the wrong target name.
* config/te-cloudabi.h: New file.
* config/tc-aarch64.c (aarch64_after_parse_args): Use TE_CLOUDABI
rather than TARGET_OS to select cloudabi.
* config/tc-i386.h (ELF_TARGET_FORMAT64): Define for TE_CLOUDABI.
* configure.tgt (*-*-cloudabi*): Set em=cloudabi.
Alan Modra