Enable last_green testing and buildifier on Buildkite and remove test…

…ing from Travis.

This only removes the relevant entries from the Travis testing matrix; we'll follow up with more Travis script cleanup later.

RELNOTES: None.
PiperOrigin-RevId: 235775646

.bazelci/presubmit.yml

@@ -1,18 +1,50 @@
 ---
-platforms:
-  macos:
+tasks:
+  macos_latest:
+    platform: macos
+    bazel: latest
+    build_targets:
+      - "//examples/..."
+    test_targets:
+      - "//examples/..."
+
+  macos_last_green:
+    platform: macos
+    bazel: last_green
+    build_targets:
+      - "//examples/..."
+    test_targets:
+      - "//examples/..."
+
+  ubuntu1804_latest:
+    platform: ubuntu1804
+    bazel: latest
     environment:
       CC: clang
+    build_flags:
+      # On Linux, we look for Swift toolchain binaries on the path. We may be
+      # able to change this when we start auto-downloading toolchains (see
+      # https://github.com/bazelbuild/rules_swift/issues/4).
+      - "--action_env=PATH"
     build_targets:
+      - "--"
       - "//examples/..."
+      - "-//examples/apple/..."
+    test_flags:
+      - "--action_env=PATH"
     test_targets:
+      - "--"
       - "//examples/..."
-  ubuntu1804:
+      - "-//examples/apple/..."
+
+  ubuntu1804_last_green:
+    platform: ubuntu1804
+    bazel: last_green
     environment:
       CC: clang
     build_flags:
-      # On Linux, we look for Swift toolchain binaries on the path. We may be able
-      # to change this when we start auto-downloading toolchains (see
+      # On Linux, we look for Swift toolchain binaries on the path. We may be
+      # able to change this when we start auto-downloading toolchains (see
       # https://github.com/bazelbuild/rules_swift/issues/4).
       - "--action_env=PATH"
     build_targets:
@@ -25,3 +57,5 @@ platforms:
       - "--"
       - "//examples/..."
       - "-//examples/apple/..."
+
+buildifier: true

.travis.yml

@@ -20,16 +20,6 @@ matrix:
       sudo: false
       env: BUILDIFIER=RELEASE
 
-    - os: linux
-      dist: trusty
-      sudo: required
-      env:
-        - BAZEL=HEAD SWIFT_VERSION=4.2.1 CC=clang TARGETS="//examples/... -//examples/apple/..."
-    - os: osx
-      osx_image: xcode10.1
-      env:
-        - BAZEL=HEAD TARGETS=//examples/...
-
 before_install:
   - .travis/install.sh