When trying to use  IMAGE_FSTYPES += "elf" fails due missing cpio.gz file, also on current master there is another failure due elf is trying to use "virtual/kernel-native" but a patch is already on the list [1], so to get this failure on apply first that patch.

1- https://patchwork.openembedded.org/patch/141623/ 

Steps:

1. Add the following variables to "conf/local.conf"
   IMAGE_FSTYPES += " elf"   
2. Compile
   $ bitbake core-image-minimal

Expected result:
The compilation process should be performed successfully and the generated compressed image should be at: "~/tmp/deploy/images/<machine>/"

Actual result:
The compilation image process failed getting the following error message:

=====================
DEBUG: Python function extend_recipe_sysroot finished
| DEBUG: Executing shell function do_image_elf
| Cannot open `/home/jgperezc/poky-contrib/build-bug10745/tmp/deploy/images/qemux86/core-image-minimal-qemux86.cpio.gz': No such file or directory
| WARNING: /home/jgperezc/poky-contrib/build-bug10745/tmp/work/qemux86-poky-linux/core-image-minimal/1.0-r0/temp/run.do_image_elf.33339:1 exit 1 from 'mkelfImage --kernel=/home/jgperezc/poky-contrib/build-bug10745/tmp/deploy/images/qemux86/bzImage --initrd=/home/jgperezc/poky-contrib/build-bug10745/tmp/deploy/images/qemux86/core-image-minimal-qemux86.cpio.gz --output=/home/jgperezc/poky-contrib/build-bug10745/tmp/work/qemux86-poky-linux/core-image-minimal/1.0-r0/deploy-core-image-minimal-image-complete/core-image-minimal-qemux86-20170706162939.rootfs.elf --append='ramdisk_size=32768 root=/dev/ram0 rw console=''