travis: add basic build test

QubesOS/qubes-issues#1926

.travis.yml

@@ -0,0 +1,11 @@
+sudo: required
+dist: trusty
+language: generic
+install: git clone https://github.com/QubesOS/qubes-builder ~/qubes-builder
+script: 
+ - ~/qubes-builder/scripts/travis-build
+ - travis_wait 30 make -C ~/qubes-builder iso BUILDERCONF=scripts/travis-builder.conf VERBOSE=0 COMPONENTS=installer-qubes-os
+after_script:
+ - tail -n 1000 ~/qubes-builder/build-logs/installer-qubes-os-iso-*.log
+env:
+  DIST_DOM0=fc20 INSTALLER_KICKSTART=/tmp/qubes-installer/conf/travis-iso.ks USE_QUBES_REPO_VERSION=3.1

conf/travis-iso.ks

@@ -0,0 +1,3 @@
+%include qubes-kickstart.cfg
+
+repo --name=qubes-r3.1-testing --gpgkey=file:///tmp/qubes-installer/qubes-release/RPM-GPG-KEY-qubes-3.1-primary --baseurl=http://yum.qubes-os.org/r3.1/current-testing/dom0/fc20