travis: Manually export TRAVIS=true for linux builds
travis: Manually export TRAVIS=true for linux builds

Docker wipes the environment before starting a build, so TRAVIS doesn't
get set and our run_tests.py script doesn't print logs for failing
tests.

trhd/meson,MathieuDuponchelle/meson,fmuellner/meson,mesonbuild/meson,wberrier/meson,QuLogic/meson,thiblahute/meson,mesonbuild/meson,ernestask/meson,rhd/meson,QuLogic/meson,becm/meson,ernestask/meson,jeandet/meson,pexip/meson,rhd/meson,ernestask/meson,wberrier/meson,centricular/meson,MathieuDuponchelle/meson,rhd/meson,centricular/meson,trhd/meson,jpakkane/meson,fmuellner/meson,mesonbuild/meson,pexip/meson,becm/meson,MathieuDuponchelle/meson,trhd/meson,jeandet/meson,centricular/meson,QuLogic/meson,pexip/meson,centricular/meson,QuLogic/meson,jpakkane/meson,rhd/meson,fmuellner/meson,thiblahute/meson,aaronp24/meson,QuLogic/meson,mesonbuild/meson,wberrier/meson,mesonbuild/meson,trhd/meson,becm/meson,MathieuDuponchelle/meson,mesonbuild/meson,thiblahute/meson,jpakkane/meson,QuLogic/meson,aaronp24/meson,becm/meson,pexip/meson,aaronp24/meson,MathieuDuponchelle/meson,becm/meson,fmuellner/meson,jpakkane/meson,trhd/meson,jpakkane/meson,ernestask/meson,mesonbuild/meson,jpakkane/meson,MathieuDuponchelle/meson,jeandet/meson,jeandet/meson,jeandet/meson,pexip/meson,wberrier/meson,ernestask/meson,jeandet/meson,aaronp24/meson,ernestask/meson,mesonbuild/meson,rhd/meson,aaronp24/meson,pexip/meson,ernestask/meson,thiblahute/meson,trhd/meson,fmuellner/meson,fmuellner/meson,aaronp24/meson,MathieuDuponchelle/meson,becm/meson,mesonbuild/meson,mesonbuild/meson,jeandet/meson,becm/meson,trhd/meson,fmuellner/meson,trhd/meson,ernestask/meson,thiblahute/meson,wberrier/meson,aaronp24/meson,jpakkane/meson,becm/meson,rhd/meson,centricular/meson,trhd/meson,QuLogic/meson,QuLogic/meson,wberrier/meson,thiblahute/meson,wberrier/meson,pexip/meson,jpakkane/meson,thiblahute/meson,MathieuDuponchelle/meson,becm/meson,rhd/meson,fmuellner/meson,aaronp24/meson,centricular/meson,ernestask/meson,QuLogic/meson,pexip/meson,pexip/meson,centricular/meson,jpakkane/meson,jeandet/meson,centricular/meson,MathieuDuponchelle/meson,pexip/meson,becm/meson,thiblahute/meson,jeandet/meson,fmuellner/meson,rhd/meson,wberrier/meson,aaronp24/meson,thiblahute/meson