Skip debug build to get cache populated.

After nearly 4 weeks Travis-CI and I still not found the cause of
the full build failing when vcpkg builds the dependencies. Time
for drastic measures.

scripts/build_macos.sh

@@ -113,7 +113,7 @@ IFS=, ; for config in $CONFIGURATION
 do
   IFS=$oldifs # Because of ; IFS set above will still be present.
   # Build and test
-  #if [ "$config" = "Debug" ]; then continue; fi
+  if [ "$config" = "Debug" ]; then continue; fi
   echo "Build KTX-Software (macOS $ARCHS $config)"
   if [ -n "$MACOS_CERTIFICATES_P12" -a "$config" = "Release" ]; then
     cmake --build . --config $config | handle_compiler_output