package/ci: use an image that doesn't have crashy nodejs.

Brittle web stuff gotta be brittle. Ugh.

package/ci/travis.yml

@@ -113,14 +113,20 @@ matrix:
     - TARGET_GLES2=OFF
   - language: cpp
     os: osx
-    osx_image: xcode9.3
+    # Since August 1st, 2019, tests that iterate over 65536 elements
+    # (MathHalfTest, MathPackingTest and MathColorTest) are segfaulting on the
+    # xcode9.3 image. Using whatever image is the default instead.
+    #osx_image: xcode9.3
     env:
     - JOBID=emscripten-webgl1
     - TARGET=emscripten
     - TARGET_GLES2=ON
   - language: cpp
     os: osx
-    osx_image: xcode9.3
+    # Since August 1st, 2019, tests that iterate over 65536 elements
+    # (MathHalfTest, MathPackingTest and MathColorTest) are segfaulting on the
+    # xcode9.3 image. Using whatever image is the default instead.
+    #osx_image: xcode9.3
     env:
     - JOBID=emscripten-webgl2
     - TARGET=emscripten