travis: update one OSX case to use latest img version

Author: xdelaruelle

.travis.yml

@@ -287,8 +287,9 @@ jobs:
       os: osx
 
     # need to specify where to find tclConfig.sh on newer xcode release
-    - env: CONFIGURE_OPTS='--prefix=/tmp/modules --enable-compat-version --with-loadedmodules=null:dot --with-tcl=/System/Library/Frameworks/Tcl.framework/Versions/8.5'
+    - env: CONFIGURE_OPTS='--prefix=/tmp/modules --enable-compat-version --with-loadedmodules=null:dot --with-tcl=/Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk/System/Library/Frameworks/Tcl.framework/Versions/8.5'
       os: osx
+      osx_image: xcode11.4
 
 
 env: