Bring back buildah pipeline in travis

.travis.yml

@@ -2,14 +2,14 @@ sudo: required
 dist: xenial
 
 env:
- - TRAVIS_PIPELINE=docker
-## TODO: figure out why buildah pipeline is flaky, even with sudo
-## - TRAVIS_PIPELINE=buildah
+ - USE_CACHE=true TRAVIS_PIPELINE=docker
+ - USE_CACHE=true TRAVIS_PIPELINE=buildah BUILDAH_LAYERS=true
 
 language: go
 
 go:
  - 1.13.x
+ - 1.14.x
 
 services: docker
 
@@ -18,6 +18,5 @@ install:
  - go get github.com/mattn/goveralls
 
 script:
-  - ./build_danm.sh
   - ./run_uts.sh
   - $GOPATH/bin/goveralls -coverprofile=ut/coverage/coverage3.out -service=travis-ci -repotoken ZY6MA490QABNKGnJgYLi53QTDuTC4H69K

build_danm.sh

@@ -70,6 +70,7 @@ if [[ ( "$TRAVIS_PIPELINE" = "buildah" ) || ( "$TRAVIS_PIPELINE" = ""  && -x "$(
 then
   BUILD_COMMAND="buildah bud"
   TAG_COMMAND="buildah tag"
+   command -v buildah || ./.travis/install_buildah.sh
 elif [[ ( "$TRAVIS_PIPELINE" = "docker" ) || ( "$TRAVIS_PIPELINE" = ""  && -x "$(command -v docker)" ) ]]
 then
   BUILD_COMMAND="docker image build"