snapcraft-preload fails to build on arm64 and ppc64el

[jdstrand]

Using the following in snapcraft.yaml:

...
  after:
  - snapcraft-preload

only amd64, i386 and armhf build. Eg:

• amd64: https://launchpadlibrarian.net/317293325/buildlog_snap_ubuntu_xenial_amd64_review-tools_BUILDING.txt.gz
• armhf: https://launchpadlibrarian.net/317293424/buildlog_snap_ubuntu_xenial_armhf_review-tools_BUILDING.txt.gz
• i386: https://launchpadlibrarian.net/317293369/buildlog_snap_ubuntu_xenial_i386_review-tools_BUILDING.txt.gz

but other architectures fail:

• arm64: https://launchpadlibrarian.net/317293239/buildlog_snap_ubuntu_xenial_arm64_review-tools_BUILDING.txt.gz
• ppc64el https://launchpadlibrarian.net/317293236/buildlog_snap_ubuntu_xenial_ppc64el_review-tools_BUILDING.txt.gz

Recent updates seem to cause arm64 and ppc64el to fail. I used to be able to use this in the snapcraft.yaml for armhf, arm64, i386 and ppc64el to build:

preload:
  source: https://github.com/sergiusens/snapcraft-preload.git
  source-commit: fc60c1d58bdb90a98622179fd3ecfdf9e35e57c3
  source-type: git
  plugin: cmake

and this for amd64:

preload:
  source: https://github.com/sergiusens/snapcraft-preload.git
  source-commit: fc60c1d58bdb90a98622179fd3ecfdf9e35e57c3
  source-type: git
  plugin: cmake
  # Uncomment the following for amd64 (LP: #1671238)
  build-packages:
  - libc6-dev-i386
  - libc6-dev-x32
  - gcc-5-multilib
  - gcc-multilib