On Mac, when 'gn args out/<bld dir>' run with 'icu_use_data_file = false' fails with the following error:

$ gn args out/rel
Waiting for editor on "/Volumes/Works/cr/t/src/out/rel/args.gn"...
Generating files...
ERROR Input to targets not generated by a dependency.
The file:
  //out/rel/icudtl.dat
is listed as an input or source for the targets:
  //remoting/host:remoting_host_resources
  //remoting/host/it2me:remote_assistance_host_resources
  //chrome:chrome_framework_resources
  //content/shell:content_shell_framework_resources
  //remoting/host:remoting_me2me_host
  //remoting/host/it2me:remote_assistance_host
  //content/shell:content_shell_framework
  //chrome:chrome_framework
but no targets in the build generate that file.

If you have generated inputs, there needs to be a dependency path between the
two targets in addition to just listing the files. For indirect dependencies,
the intermediate ones must be public_deps. data_deps don't count since they're
only runtime dependencies. If you think a dependency chain exists, it might be
because the chain is private. Try "gn path" to analyze.
---------------



BTW, here's the output from 'gn path' 
$ gn path out/rel //chrome:chrome_framework_resources   //third_party/icu:icudata --all
//chrome:chrome_framework_resources --[public]-->
//third_party/icu:icudata

//chrome:chrome_framework_resources --[public]-->
//third_party/icu:icudata

//chrome:chrome_framework_resources --[public]-->
//v8:v8 --[public]-->
//v8:v8_base --[private]-->
//third_party/icu:icu --[public]-->
//third_party/icu:icuuc --[private]-->
//third_party/icu:icudata

//chrome:chrome_framework_resources --[public]-->
//v8:v8 --[public]-->
//v8:v8_maybe_snapshot --[public]-->
//v8:v8_external_snapshot --[public]-->
//v8:run_mksnapshot --[private]-->
//v8:mksnapshot --[private]-->
//v8:v8_base --> see private chain printed above...

//chrome:chrome_framework_resources --[public]-->
//v8:v8 --[public]-->
//v8:v8_maybe_snapshot --[public]-->
//v8:v8_external_snapshot --[public]-->
//v8:run_mksnapshot --[private]-->
//v8:mksnapshot --[private]-->
//v8:v8_nosnapshot --[private]-->
//v8:v8_base --> see private chain printed above...
---------------------------------------------------------

The issue is that the targets listed above (for gn args ) list 'icudtl.dat' as 'source' unconditionally. When I tried to make it conditional upon 'icu_use_data_file', GN complained that the variable icu_use_data_file is not declared. 


Some users of third_party/icu (e.g. some embeddeers of v8, and some builds of Windows. And, Android webview is another customer IIRC ) may still want to keep that option viable so that it has to be kept in BUILD.gn for third_party/icu. 

Mac may not need that option. (I haven't tried that option on Mac for a long while even with gyp. I'm trying it now).