travis/osx: Fix pkg-config installation

To get better test coverage, we were installing pkg-config in one
branch and not installing it in the other. This broke when qt started
pulling in pkg-config in Homebrew.

.travis.yml

@@ -41,9 +41,9 @@ matrix:
 before_install:
   - python ./skip_ci.py --base-branch-env=TRAVIS_BRANCH --is-pull-env=TRAVIS_PULL_REQUEST
   - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then brew update; fi
+    # # Run one macOS build with pkg-config available (pulled in by qt), and the other (unity=off) with pkg-config
   - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then brew install qt ldc llvm ninja; fi
-    # # Run one macOS build without pkg-config available, and the other (unity=on) with pkg-config
-  - if [[ "$TRAVIS_OS_NAME" == "osx" && "$MESON_ARGS" =~ .*unity=on.* ]]; then brew install pkg-config; fi
+  - if [[ "$TRAVIS_OS_NAME" == "osx" && "$MESON_ARGS" =~ .*unity=on.* ]]; then chmod -x `which pkg-config`; fi
   - if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then docker pull jpakkane/mesonci:eoan; fi
 
 # We need to copy the current checkout inside the Docker container,