Explicitly run four macOS jobs

Author: kulp

.travis.yml

@@ -3,6 +3,9 @@ language: rust
 os:
   - linux
 
+# Force use of macOS 10.14 Mojave until Catalina is made to work for us.
+osx_image: xcode11.3
+
 rust:
   - stable
 
@@ -72,6 +75,18 @@ env:
 matrix:
   fast_finish: true
 
+  # Include a few jobs for spot-checking different configurations without
+  # invoking combinatoric explosion of Travis jobs.
+  include:
+    - os: osx
+      env: LLVM_VERSION="9.0" BINDGEN_JOB="test"         BINDGEN_PROFILE=
+    - os: osx
+      env: LLVM_VERSION="9.0" BINDGEN_JOB="test"         BINDGEN_PROFILE="--release"
+    - os: osx
+      env: LLVM_VERSION="9.0" BINDGEN_JOB="integration"  BINDGEN_PROFILE=
+    - os: osx
+      env: LLVM_VERSION="9.0" BINDGEN_JOB="integration"  BINDGEN_PROFILE="--release"
+
 cache:
   directories:
     - $HOME/.cargo