Make use of Travis's conditional jobs.

[kennytm]

Conditional jobs: https://docs.travis-ci.com/user/conditional-builds-stages-jobs/#Conditional-Jobs.

Jobs not matching the condition will not be scheduled at all. This allows us to get rid of $ALLOW_PR/$ALLOW_TRY/$SKIP_BUILD in .travis.yml, and perfectly prevent spurious PR failures due to flaky macOS machines.

[kennytm]

@bors try

Let me verify if the try build works before merging.

[bors]

⌛ Trying commit 9f76354 with merge f0b4249...

[kennytm]

OK try build works (?). The remaining thing is to ensure all 41 jobs are running during the actual test.

---

EDIT: Not sure if relevant, but the try build failed to download the cache archive, causing 45 minutes spent on building docker. Maybe just due to removing the ALLOW_TRY=1/ALLOW_PR=1 from env.

attempting to download cache archive
fetching try/cache-linux-trusty-70f9407258c60900855a3084c00fd20c656cf873dba281d668f25c4bced6e8fc.tgz
fetching master/cache-linux-trusty-70f9407258c60900855a3084c00fd20c656cf873dba281d668f25c4bced6e8fc.tgz
could not download cache

[Mark-Simulacrum]

r? @alexcrichton

r=me, but I want to run this past you as well.

cc @rust-lang/infra as well.

[bors]

☀️ Test successful - status-travis
State: approved= try=True

[TimNN]

@kennytm:

EDIT: Not sure if relevant, but the try build failed to download the cache archive. Maybe just due to removing the ALLOW_TRY=1/ALLOW_PR=1 from env.

That seems to be the case, see https://docs.travis-ci.com/user/caching/#Caches-and-build-matrices

[alexcrichton]

@bors: r+

Nice find!

[bors]

📌 Commit 9f76354 has been approved by alexcrichton