Disable Travis OSX ruby and tcl builds

These have started to fail since XCode was upgraded to 9.4

.travis.yml

@@ -370,6 +370,15 @@ matrix:
       env: SWIGLANG=python SWIG_FEATURES=-O
       sudo: required
       dist: trusty
+    # Broken since Travis image moved from Xcode 8.3 to 9.4
+    - compiler: clang
+      os: osx
+      env: SWIGLANG=ruby
+    # Broken since Travis image moved from Xcode 8.3 to 9.4
+    - compiler: clang
+      os: osx
+      env: SWIGLANG=tcl
+
 before_install:
   - date -u
   - uname -a