Travis: Keep the macOS Rust job, but don't wait for it to finish

Since Rust on macOS is slow, don't wait for the macOS Rust job to finish.
Instead, split rust into slow rust (macOS) and fast rust (Linux). And
allow the build to finish before slow rust finishes.

Also make sure that we have:
* a Rust build on each platform,
* a Rust build with each compiler, and
* a check on all our Rust builds.

Finally, sort builds: allow fail last, macOS first, slowest first.

Closes 31859 for 0.3.5.

.travis.yml

@@ -37,25 +37,30 @@ matrix:
     ## We run basic tests on macOS
     - compiler: clang
       os: osx
+    ## We check NSS
+    ## NSS is a fast job, clang is slower on Linux, so we do NSS clang
+    - env: NSS_OPTIONS="--enable-nss"
+      compiler: clang
     ## We run chutney on Linux, because it's faster than chutney on macOS
     - env: CHUTNEY="yes" CHUTNEY_ALLOW_FAILURES="2" SKIP_MAKE_CHECK="yes"
-    ## We check asciidoc with distcheck, to make sure we remove doc products
-    - env: DISTCHECK="yes" ASCIIDOC_OPTIONS="" SKIP_MAKE_CHECK="yes"
     ## We include a single coverage build with the best options for coverage
     - env: COVERAGE_OPTIONS="--enable-coverage" HARDENING_OPTIONS=""
-    ## We run chutney on macOS, because macOS Travis has IPv6
-    - env: CHUTNEY="yes" CHUTNEY_ALLOW_FAILURES="2" SKIP_MAKE_CHECK="yes"
-      os: osx
-    ## We clone our stem repo and run `make test-stem`
-    - env: TEST_STEM="yes" SKIP_MAKE_CHECK="yes"
+    ## We run rust on Linux, because it's faster than rust on macOS
+    ## We check rust offline
+    - env: RUST_OPTIONS="--enable-rust" TOR_RUST_DEPENDENCIES=true
+    ## We check asciidoc with distcheck, to make sure we remove doc products
+    - env: DISTCHECK="yes" ASCIIDOC_OPTIONS="" SKIP_MAKE_CHECK="yes"
     ## We check disable module dirauth
     - env: MODULES_OPTIONS="--disable-module-dirauth"
     ## We run rust on macOS, because we have seen macOS rust failures before
     - env: RUST_OPTIONS="--enable-rust --enable-cargo-online-mode"
       compiler: clang
       os: osx
-    ## We check NSS
-    - env: NSS_OPTIONS="--enable-nss"
+    ## We run chutney on macOS, because macOS Travis has IPv6
+    - env: CHUTNEY="yes" CHUTNEY_ALLOW_FAILURES="2" SKIP_MAKE_CHECK="yes"
+      os: osx
+    ## We clone our stem repo and run `make test-stem`
+    - env: TEST_STEM="yes" SKIP_MAKE_CHECK="yes"
 
   ## Allow the build to report success (with non-required sub-builds
   ## continuing to run) if all required sub-builds have succeeded.
@@ -64,9 +69,12 @@ matrix:
   ## Careful! We use global envs, which makes it hard to allow failures by env:
   ## https://docs.travis-ci.com/user/customizing-the-build#matching-jobs-with-allow_failures
   allow_failures:
-    ## macOS chutney is very slow, so we let the build finish before it's done
-    ## We'd like to fast finish, but still eventually show failures.
-    ## But Travis doesn't have that option.
+    ## macOS rust and chutney are very slow, so we let the build finish before
+    ## they are done.  We'd like to fast finish, but still eventually show
+    ## any failures in the build status. But Travis doesn't have that ability.
+    - env: RUST_OPTIONS="--enable-rust --enable-cargo-online-mode"
+      compiler: clang
+      os: osx
     - env: CHUTNEY="yes" CHUTNEY_ALLOW_FAILURES="2" SKIP_MAKE_CHECK="yes"
       os: osx
     ## test-stem sometimes hangs on Travis